diff --git a/powershell/ql/lib/semmle/code/powershell/ast/internal/ChildIndex.qll b/powershell/ql/lib/semmle/code/powershell/ast/internal/ChildIndex.qll
index df29eb7f516d..4acc6683d767 100644
--- a/powershell/ql/lib/semmle/code/powershell/ast/internal/ChildIndex.qll
+++ b/powershell/ql/lib/semmle/code/powershell/ast/internal/ChildIndex.qll
@@ -33,11 +33,14 @@ newtype ChildIndex =
   } or
   ThisVar() or
   PipelineParamVar() or
-  // PipelineByPropertNameVar(Raw::PipelineByPropertyNameParameter p) or
+  PipelineByPropertyNameVar(Raw::PipelineByPropertyNameParameter p) or
   PipelineIteratorVar() or
   PipelineByPropertyNameIteratorVar(Raw::PipelineByPropertyNameParameter p) or
   RealVar(string name) { name = variableNameInScope(_, _) } or
-  ProcessBlockPipelineVarReadAccess()
+  ProcessBlockPipelineVarReadAccess() or
+  ProcessBlockPipelineByPropertyNameVarReadAccess(string name) {
+    name = any(Raw::PipelineByPropertyNameParameter p).getName()
+  }
 
 int synthPipelineParameterChildIndex(Raw::ScriptBlock sb) {
   // If there is a parameter block, but no pipeline parameter
@@ -340,3 +343,7 @@ ChildIndex whileStmtCond() { result = RawChildIndex(Raw::WhileStmtCond()) }
 ChildIndex whileStmtBody() { result = RawChildIndex(Raw::WhileStmtBody()) }
 
 ChildIndex processBlockPipelineVarReadAccess() { result = ProcessBlockPipelineVarReadAccess() }
+
+ChildIndex processBlockPipelineByPropertyNameVarReadAccess(string name) {
+  result = ProcessBlockPipelineByPropertyNameVarReadAccess(name)
+}
diff --git a/powershell/ql/lib/semmle/code/powershell/ast/internal/NamedBlock.qll b/powershell/ql/lib/semmle/code/powershell/ast/internal/NamedBlock.qll
index 10da368db65e..5e721df9de14 100644
--- a/powershell/ql/lib/semmle/code/powershell/ast/internal/NamedBlock.qll
+++ b/powershell/ql/lib/semmle/code/powershell/ast/internal/NamedBlock.qll
@@ -58,7 +58,20 @@ class ProcessBlock extends NamedBlock {
     synthChild(getRawAst(this), processBlockPipelineVarReadAccess(), result)
   }
 
+  PipelineByPropertyNameParameter getPipelineByPropertyNameParameter(string name) {
+    result = scriptBlock.getAParameter() and
+    result.getPropertyName() = name
+  }
+
   PipelineByPropertyNameParameter getAPipelineByPropertyNameParameter() {
-    result = scriptBlock.getEnclosingFunction().getAParameter()
+    result = this.getPipelineByPropertyNameParameter(_)
+  }
+
+  VarReadAccess getPipelineByPropertyNameParameterAccess(string name) {
+    synthChild(getRawAst(this), processBlockPipelineByPropertyNameVarReadAccess(name), result)
+  }
+
+  VarReadAccess getAPipelineByPropertyNameParameterAccess() {
+    result = this.getPipelineByPropertyNameParameterAccess(_)
   }
 }
diff --git a/powershell/ql/lib/semmle/code/powershell/ast/internal/Synthesis.qll b/powershell/ql/lib/semmle/code/powershell/ast/internal/Synthesis.qll
index 30356666b25f..2fee3dd99d6a 100644
--- a/powershell/ql/lib/semmle/code/powershell/ast/internal/Synthesis.qll
+++ b/powershell/ql/lib/semmle/code/powershell/ast/internal/Synthesis.qll
@@ -615,7 +615,7 @@ private module LiteralSynth {
 
   /**
    * Holds if `va` is an access to the automatic variable named `name`.
-   * 
+   *
    * Unlike `Raw::isAutomaticVariableAccess`, this predicate also checks for
    * shadowing.
    */
@@ -770,6 +770,13 @@ private module IteratorAccessSynth {
         or
         va.getUserPath().toLowerCase() =
           pb.getScriptBlock().getParamBlock().getPipelineParameter().getName().toLowerCase()
+        or
+        va.getUserPath().toLowerCase() =
+          pb.getScriptBlock()
+              .getParamBlock()
+              .getAPipelineByPropertyNameParameter()
+              .getName()
+              .toLowerCase()
       )
     }
 
@@ -867,12 +874,19 @@ private module PipelineAccess {
           pipelineVar = TVariableSynth(pb.getScriptBlock(), PipelineParamVar()) and
           child = SynthChild(VarAccessSynthKind(pipelineVar))
         )
+        or
+        exists(PipelineByPropertyNameVariable pipelineVar, Raw::PipelineByPropertyNameParameter p |
+          i = processBlockPipelineByPropertyNameVarReadAccess(p.getName()) and
+          getResultAst(p) = pipelineVar and
+          child = SynthChild(VarAccessSynthKind(pipelineVar))
+        )
       )
     }
 
     final override Location getLocation(Ast n) {
       exists(ProcessBlock pb |
-        pb.getPipelineParameterAccess() = n and
+        pb.getPipelineParameterAccess() = n or pb.getAPipelineByPropertyNameParameterAccess() = n
+      |
         result = pb.getLocation()
       )
     }
@@ -881,6 +895,23 @@ private module PipelineAccess {
       exists(ProcessBlock pb |
         pb.getPipelineParameterAccess() = va and
         v = pb.getPipelineParameter()
+        or
+        exists(string name |
+          pb.getPipelineByPropertyNameParameterAccess(name) = va and
+          v = pb.getPipelineByPropertyNameParameter(name)
+        )
+      )
+    }
+  }
+}
+
+private module ImplicitAssignmentInForEach {
+  private class ForEachAssignment extends Synthesis {
+    override predicate implicitAssignment(Raw::Ast dest, string name) {
+      exists(Raw::ForEachStmt forEach, Raw::VarAccess va |
+        va = forEach.getVarAccess() and
+        va = dest and
+        va.getUserPath() = name
       )
     }
   }
diff --git a/powershell/ql/lib/semmle/code/powershell/ast/internal/Variable.qll b/powershell/ql/lib/semmle/code/powershell/ast/internal/Variable.qll
index c843a4ac52a7..c1d0a53edfbb 100644
--- a/powershell/ql/lib/semmle/code/powershell/ast/internal/Variable.qll
+++ b/powershell/ql/lib/semmle/code/powershell/ast/internal/Variable.qll
@@ -45,7 +45,9 @@ module Private {
 
   class ParameterImpl extends VariableSynth {
     ParameterImpl() {
-      i instanceof FunParam or i instanceof PipelineParamVar or i instanceof ThisVar
+      i instanceof FunParam or
+      i instanceof PipelineParamVar or
+      i instanceof ThisVar
     }
   }
 
@@ -59,6 +61,14 @@ module Private {
     ScriptBlock getScriptBlock() { this = TVariableSynth(getRawAst(result), _) }
   }
 
+  class PipelineByPropertyNameVariableImpl extends ParameterImpl {
+    PipelineByPropertyNameVariableImpl() {
+      getRawAst(this) instanceof Raw::PipelineByPropertyNameParameter
+    }
+
+    ScriptBlock getScriptBlock() { this = TVariableSynth(getRawAst(result), _) }
+  }
+
   class PipelineIteratorVariableImpl extends VariableSynth {
     override PipelineIteratorVar i;
 
@@ -171,6 +181,11 @@ module Public {
     ScriptBlock getScriptBlock() { result = super.getScriptBlock() }
   }
 
+  class PipelineByPropertyNameVariable extends Variable instanceof PipelineByPropertyNameVariableImpl
+  {
+    ScriptBlock getScriptBlock() { result = super.getScriptBlock() }
+  }
+
   class PipelineIteratorVariable extends Variable instanceof PipelineIteratorVariableImpl {
     ProcessBlock getProcessBlock() { result = super.getProcessBlock() }
   }
diff --git a/powershell/ql/lib/semmle/code/powershell/controlflow/CfgNodes.qll b/powershell/ql/lib/semmle/code/powershell/controlflow/CfgNodes.qll
index c8126a68ab97..58ca40b5e714 100644
--- a/powershell/ql/lib/semmle/code/powershell/controlflow/CfgNodes.qll
+++ b/powershell/ql/lib/semmle/code/powershell/controlflow/CfgNodes.qll
@@ -277,6 +277,8 @@ private class ProcessBlockChildMapping extends NamedBlockChildMapping, ProcessBl
     super.relevantChild(child)
     or
     child = super.getPipelineParameterAccess()
+    or
+    child = super.getAPipelineByPropertyNameParameterAccess()
   }
 }
 
@@ -300,6 +302,23 @@ class ProcessBlockCfgNode extends NamedBlockCfgNode {
   PipelineIteratorVariable getPipelineIteratorVariable() {
     result.getProcessBlock().getScriptBlock() = this.getScriptBlock().getAstNode()
   }
+
+  PipelineByPropertyNameIteratorVariable getPipelineBypropertyNameIteratorVariable(string name) {
+    result.getPropertyName() = name and
+    result.getProcessBlock().getScriptBlock() = this.getScriptBlock().getAstNode()
+  }
+
+  PipelineByPropertyNameIteratorVariable getAPipelineBypropertyNameIteratorVariable() {
+    result = this.getPipelineBypropertyNameIteratorVariable(_)
+  }
+
+  ExprNodes::VarReadAccessCfgNode getPipelineByPropertyNameParameterAccess(string name) {
+    block.hasCfgChild(block.getPipelineByPropertyNameParameterAccess(name), this, result)
+  }
+
+  ExprNodes::VarReadAccessCfgNode getAPipelineByPropertyNameParameterAccess() {
+    result = this.getPipelineByPropertyNameParameterAccess(_)
+  }
 }
 
 private class CatchClauseChildMapping extends NonExprChildMapping, CatchClause {
diff --git a/powershell/ql/lib/semmle/code/powershell/controlflow/internal/Completion.qll b/powershell/ql/lib/semmle/code/powershell/controlflow/internal/Completion.qll
index 68b602dfd93e..d551b674fbad 100644
--- a/powershell/ql/lib/semmle/code/powershell/controlflow/internal/Completion.qll
+++ b/powershell/ql/lib/semmle/code/powershell/controlflow/internal/Completion.qll
@@ -188,7 +188,11 @@ private predicate inMatchingContext(Ast n) {
  * Holds if a normal completion of `cfe` must be an emptiness completion. Thats is,
  * whether `cfe` determines whether to execute the body of a `foreach` statement.
  */
-private predicate mustHaveEmptinessCompletion(Ast n) { n instanceof ForEachStmt }
+private predicate mustHaveEmptinessCompletion(Ast n) {
+  n instanceof ForEachStmt
+  or
+  any(CfgImpl::Trees::ProcessBlockTree pbtree).lastEmptinessCheck(n)
+}
 
 /**
  * A completion that represents normal evaluation of a statement or an
diff --git a/powershell/ql/lib/semmle/code/powershell/controlflow/internal/ControlFlowGraphImpl.qll b/powershell/ql/lib/semmle/code/powershell/controlflow/internal/ControlFlowGraphImpl.qll
index d28828481f56..e9c5c4862e4d 100644
--- a/powershell/ql/lib/semmle/code/powershell/controlflow/internal/ControlFlowGraphImpl.qll
+++ b/powershell/ql/lib/semmle/code/powershell/controlflow/internal/ControlFlowGraphImpl.qll
@@ -221,13 +221,7 @@ module Trees {
       or
       last(super.getProcessBlock(), pred, c) and
       completionIsNormal(c) and
-      (
-        // If we process multiple items we will loop back to the process block
-        first(super.getProcessBlock(), succ)
-        or
-        // Once we're done process all items we will go to the end block
-        first(super.getEndBlock(), succ)
-      )
+      first(super.getEndBlock(), succ)
     }
 
     final override predicate propagatesAbnormal(AstNode child) {
@@ -292,25 +286,17 @@ module Trees {
     final override predicate succEntry(Ast n, Completion c) { n = this and completionIsSimple(c) }
   }
 
-  abstract class NamedBlockTreeBase extends ControlFlowTree instanceof NamedBlock {
-    final override predicate last(Ast last, Completion c) {
+  abstract class NamedBlockTreeBase extends PreOrderTree instanceof NamedBlock {
+    override predicate last(Ast last, Completion c) {
       exists(int i | last(super.getStmt(i), last, c) |
         completionIsNormal(c) and
         not exists(super.getStmt(i + 1))
         or
         not completionIsNormal(c)
       )
-      or
-      not exists(super.getAStmt()) and
-      completionIsSimple(c) and
-      last = this
     }
 
     override predicate succ(Ast pred, Ast succ, Completion c) {
-      pred = this and
-      completionIsSimple(c) and
-      first(super.getStmt(0), succ)
-      or
       exists(int i |
         last(super.getStmt(i), pred, c) and
         completionIsNormal(c) and
@@ -324,20 +310,85 @@ module Trees {
   class NamedBlockTree extends NamedBlockTreeBase instanceof NamedBlock {
     NamedBlockTree() { not this instanceof ProcessBlock }
 
-    final override predicate first(Ast first) { first = this }
+    final override predicate last(Ast last, Completion c) {
+      super.last(last, c)
+      or
+      not exists(super.getAStmt()) and
+      completionIsSimple(c) and
+      last = this
+    }
+
+    final override predicate succ(Ast pred, Ast succ, Completion c) {
+      pred = this and
+      completionIsSimple(c) and
+      first(super.getStmt(0), succ)
+      or
+      super.succ(pred, succ, c)
+    }
 
     final override predicate propagatesAbnormal(Ast child) { super.propagatesAbnormal(child) }
   }
 
+  private VarAccess getRankedPipelineByPropertyNameVariable(ProcessBlock pb, int i) {
+    result =
+      rank[i + 1](string name | | pb.getPipelineByPropertyNameParameterAccess(name) order by name)
+  }
+
   class ProcessBlockTree extends NamedBlockTreeBase instanceof ProcessBlock {
-    final override predicate first(Ast first) { first = super.getPipelineParameterAccess() }
+    predicate lastEmptinessCheck(AstNode last) {
+      last = super.getPipelineParameterAccess() and
+      not exists(super.getAPipelineByPropertyNameParameterAccess())
+      or
+      exists(int i |
+        last = getRankedPipelineByPropertyNameVariable(this, i) and
+        not exists(getRankedPipelineByPropertyNameVariable(this, i + 1))
+      )
+    }
+
+    private predicate succEmptinessCheck(AstNode pred, AstNode succ, Completion c) {
+      last(super.getPipelineParameterAccess(), pred, c) and
+      first(getRankedPipelineByPropertyNameVariable(this, 0), succ)
+      or
+      exists(int i |
+        last(getRankedPipelineByPropertyNameVariable(this, i), pred, c) and
+        first(getRankedPipelineByPropertyNameVariable(this, i + 1), succ)
+      )
+    }
+
+    private predicate firstEmptinessCheck(AstNode first) {
+      first(super.getPipelineParameterAccess(), first)
+    }
+
+    final override predicate last(AstNode last, Completion c) {
+      // Emptiness test exits with no more elements
+      this.lastEmptinessCheck(last) and
+      c.(EmptinessCompletion).isEmpty()
+      or
+      super.last(last, c)
+    }
 
     final override predicate succ(Ast pred, Ast succ, Completion c) {
-      this.first(pred) and
-      completionIsSimple(c) and
-      succ = this
+      // Evaluate the pipeline access
+      pred = this and
+      this.firstEmptinessCheck(succ) and
+      completionIsSimple(c)
+      or
+      this.succEmptinessCheck(pred, succ, c)
+      or
+      this.lastEmptinessCheck(pred) and
+      c = any(EmptinessCompletion ec | not ec.isEmpty()) and
+      first(super.getStmt(0), succ)
       or
       super.succ(pred, succ, c)
+      or
+      // Body to emptiness test
+      exists(Ast last0 |
+        super.last(last0, _) and
+        last(last0, pred, c) and
+        // TODO: I don't think this correctly models the semantics inside process blocks
+        c.continuesLoop()
+      ) and
+      this.firstEmptinessCheck(succ)
     }
 
     final override predicate propagatesAbnormal(Ast child) { super.propagatesAbnormal(child) }
diff --git a/powershell/ql/lib/semmle/code/powershell/dataflow/Ssa.qll b/powershell/ql/lib/semmle/code/powershell/dataflow/Ssa.qll
index 212936b3643d..0d1b37283265 100644
--- a/powershell/ql/lib/semmle/code/powershell/dataflow/Ssa.qll
+++ b/powershell/ql/lib/semmle/code/powershell/dataflow/Ssa.qll
@@ -158,7 +158,7 @@ module Ssa {
         not exists(this.getSplitString()) and
         prefix = ""
       |
-        result = prefix + "phi"
+        result = prefix + "phi (" + this.getSourceVariable() + ")"
       )
     }
 
diff --git a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll
index f408d2ed44a4..a2437f884010 100644
--- a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll
+++ b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll
@@ -66,6 +66,8 @@ module SsaFlow {
     result = TThisParameterNode(p.asThis())
     or
     result = TPipelineParameterNode(p.asPipelineParameter())
+    or
+    result = TPipelineByPropertyNameParameterNode(p.asPipelineByPropertyNameParameter())
   }
 
   /** Gets the SSA node corresponding to the PowerShell node `n`. */
@@ -83,6 +85,16 @@ module SsaFlow {
           .definesAt(pb.getPipelineIteratorVariable(), bb, i)
     )
     or
+    exists(
+      BasicBlock bb, int i, PipelineByPropertyNameParameter p, ProcessPropertyByNameNode pbNode
+    |
+      pbNode = n and
+      pbNode.hasRead() and
+      pbNode.getParameter() = p and
+      bb.getNode(i) = pbNode.getProcessBlock() and
+      result.(Impl::SsaDefinitionNode).getDefinition().definesAt(p.getIteratorVariable(), bb, i)
+    )
+    or
     result.(Impl::ExprPostUpdateNode).getExpr() = n.(PostUpdateNode).getPreUpdateNode().asExpr()
     or
     n = toParameterNode(result.(Impl::ParameterNode).getParameter())
@@ -145,13 +157,16 @@ module LocalFlow {
       nodeTo.(ReturnNodeImpl).getCfgScope() = scriptBlock.getAstNode()
     )
     or
-    exists(CfgNodes::ExprNodes::PipelineArgumentCfgNode e | nodeFrom.asExpr() = e |
-      // If we are not already tracking as element content
-      nodeTo = TPrePipelineArgumentNode(e)
-      or
-      // If we are already tracking an element content
-      nodeTo = TPipelineArgumentNode(e)
+    nodeTo.(PreProcessPropertyByNameNode).getAccess() = nodeFrom.asExpr()
+    or
+    exists(PreProcessPropertyByNameNode pbNode |
+      pbNode = nodeFrom and
+      nodeTo = TProcessPropertyByNameNode(pbNode.getAccess().getVariable(), false)
     )
+    or
+    nodeTo.(PreProcessNode).getProcessBlock().getPipelineVariableAccess() = nodeFrom.asExpr()
+    or
+    nodeTo.(ProcessNode).getProcessBlock() = nodeFrom.(PreProcessNode).getProcessBlock()
   }
 
   predicate flowSummaryLocalStep(
@@ -179,12 +194,6 @@ module VariableCapture {
   // TODO
 }
 
-private predicate isProcessPropertyByNameNode(
-  PipelineByPropertyNameIteratorVariable iter, ProcessBlock pb
-) {
-  pb = iter.getProcessBlock()
-}
-
 /** A collection of cached types and predicates to be evaluated in the same stage. */
 cached
 private module Cached {
@@ -198,8 +207,6 @@ private module Cached {
     TThisParameterNode(Method m) or
     TPipelineByPropertyNameParameterNode(PipelineByPropertyNameParameter p) or
     TPipelineParameterNode(PipelineParameter p) or
-    TPrePipelineArgumentNode(CfgNodes::ExprNodes::PipelineArgumentCfgNode n) or
-    TPipelineArgumentNode(CfgNodes::ExprNodes::PipelineArgumentCfgNode n) or
     TExprPostUpdateNode(CfgNodes::ExprCfgNode n) {
       n instanceof CfgNodes::ExprNodes::ArgumentCfgNode
       or
@@ -220,9 +227,13 @@ private module Cached {
       blockMayReturnMultipleValues(scriptBlock)
     } or
     TReturnNodeImpl(CfgScope scope) or
+    TPreProcessNode(CfgNodes::ProcessBlockCfgNode process) or
     TProcessNode(CfgNodes::ProcessBlockCfgNode process) or
-    TProcessPropertyByNameNode(PipelineByPropertyNameIteratorVariable iter) {
-      isProcessPropertyByNameNode(iter, _)
+    TPreProcessPropertyByNameNode(CfgNodes::ExprNodes::VarReadAccessCfgNode va) {
+      any(CfgNodes::ProcessBlockCfgNode pb).getAPipelineByPropertyNameParameterAccess() = va
+    } or
+    TProcessPropertyByNameNode(PipelineByPropertyNameParameter p, Boolean hasRead) {
+      p.getDeclaringScope() = any(ProcessBlock pb).getScriptBlock()
     } or
     TScriptBlockNode(ScriptBlock scriptBlock) or
     TForbiddenRecursionGuard() {
@@ -333,15 +344,13 @@ private module Cached {
 
   cached
   newtype TContentSet =
-    TSingletonContent(Content c) or
-    TAnyElementContent() or
-    TKnownOrUnknownElementContent(Content::KnownElementContent c)
-
-  private predicate trackKnownValue(ConstantValue cv) {
-    exists(cv.asString())
-    or
-    cv.asInt() = [0 .. 10]
-  }
+    TSingletonContentSet(Content c) or
+    TAnyElementContentSet() or
+    TAnyPositionalContentSet() or
+    TKnownOrUnknownKeyContentSet(Content::KnownKeyContent c) or
+    TKnownOrUnknownPositionalContentSet(Content::KnownPositionalContent c) or
+    TUnknownPositionalElementContentSet() or
+    TUnknownKeyContentSet()
 
   cached
   newtype TContent =
@@ -350,20 +359,41 @@ private module Cached {
       or
       name = any(MemberExpr me).getMemberName()
     } or
-    TKnownElementContent(ConstantValue cv) { trackKnownValue(cv) } or
-    TUnknownElementContent()
+    // A known map key
+    TKnownKeyContent(ConstantValue cv) { exists(cv.asString()) } or
+    // A known array index
+    TKnownPositionalContent(ConstantValue cv) { cv.asInt() = [0 .. 10] } or
+    // An unknown key
+    TUnknownKeyContent() or
+    // An unknown positional element
+    TUnknownPositionalContent() or
+    // A unknown position or key - and we dont even know what kind it is
+    TUnknownKeyOrPositionContent()
 
   cached
   newtype TContentApprox =
+    // A field
     TNonElementContentApprox(Content c) { not c instanceof Content::ElementContent } or
-    TUnknownElementContentApprox() or
-    TKnownIntegerElementContentApprox() or
-    TKnownElementContentApprox(string approx) { approx = approxKnownElementIndex(_) }
+    // An unknown key
+    TUnkownKeyContentApprox() or
+    // A known map key
+    TKnownKeyContentApprox(string approx) { approx = approxKnownElementIndex(_) } or
+    // A known positional element
+    TKnownPositionalContentApprox() or
+    // An unknown positional element
+    TUnknownPositionalContentApprox() or
+    TUnknownContentApprox()
 
   cached
   newtype TDataFlowType = TUnknownDataFlowType()
 }
 
+class TKnownElementContent = TKnownKeyContent or TKnownPositionalContent;
+
+class TKnownKindContent = TUnknownPositionalContent or TUnknownKeyContent;
+
+class TUnknownElementContent = TKnownKindContent or TUnknownKeyOrPositionContent;
+
 class TElementContent = TKnownElementContent or TUnknownElementContent;
 
 /** Gets a string for approximating known element indices. */
@@ -623,10 +653,10 @@ private module ParameterNodes {
 
     PipelineByPropertyNameParameterNode() { this = TPipelineByPropertyNameParameterNode(parameter) }
 
-    override PipelineParameter getParameter() { result = parameter }
+    override PipelineByPropertyNameParameter getParameter() { result = parameter }
 
     override predicate isParameterOf(DataFlowCallable c, ParameterPosition pos) {
-      pos.isPipeline() and // what about when it is applied as a normal parameter?
+      pos.isPipeline() and
       c.asCfgScope() = parameter.getEnclosingScope()
     }
 
@@ -690,22 +720,6 @@ abstract class ArgumentNode extends Node {
   final DataFlowCall getCall() { this.argumentOf(result, _) }
 }
 
-class PrePipelineArgumentNodeImpl extends NodeImpl, TPrePipelineArgumentNode {
-  CfgNodes::ExprNodes::PipelineArgumentCfgNode e;
-
-  PrePipelineArgumentNodeImpl() { this = TPrePipelineArgumentNode(e) }
-
-  final override CfgScope getCfgScope() { result = e.getScope() }
-
-  final override Location getLocationImpl() { result = e.getLocation() }
-
-  final override string toStringImpl() { result = "[pre pipeline] " + e.toString() }
-
-  final override predicate nodeIsHidden() { any() }
-
-  CfgNodes::ExprNodes::PipelineArgumentCfgNode getPipelineArgument() { result = e }
-}
-
 module ArgumentNodes {
   class ExplicitArgumentNode extends ArgumentNode {
     CfgNodes::ExprNodes::ArgumentCfgNode arg;
@@ -749,23 +763,15 @@ module ArgumentNodes {
     }
   }
 
-  class PipelineArgumentNodeImpl extends NodeImpl, TPipelineArgumentNode {
-    CfgNodes::ExprNodes::PipelineArgumentCfgNode e;
-
-    PipelineArgumentNodeImpl() { this = TPipelineArgumentNode(e) }
-
-    final override CfgScope getCfgScope() { result = e.getScope() }
-
-    final override Location getLocationImpl() { result = e.getLocation() }
-
-    final override string toStringImpl() { result = e.toString() }
-
-    final override predicate nodeIsHidden() { none() }
+  class PipelineArgumentNode extends ArgumentNode instanceof ExprNode {
+    PipelineArgumentNode() {
+      this.getExprNode() instanceof CfgNodes::ExprNodes::PipelineArgumentCfgNode
+    }
 
-    CfgNodes::ExprNodes::PipelineArgumentCfgNode getPipelineArgument() { result = e }
-  }
+    CfgNodes::ExprNodes::PipelineArgumentCfgNode getPipelineArgument() {
+      result = super.getExprNode()
+    }
 
-  class PipelineArgumentNode extends ArgumentNode instanceof PipelineArgumentNodeImpl {
     override predicate argumentOf(DataFlowCall call, ArgumentPosition pos) {
       this.sourceArgumentOf(call.asCall(), pos)
     }
@@ -773,7 +779,7 @@ module ArgumentNodes {
     override predicate sourceArgumentOf(
       CfgNodes::ExprNodes::CallExprCfgNode call, ArgumentPosition pos
     ) {
-      call = super.getPipelineArgument().getCall() and
+      call = this.getPipelineArgument().getCall() and
       pos.isPipeline()
     }
   }
@@ -923,7 +929,7 @@ predicate storeStep(Node node1, ContentSet c, Node node2) {
       e.getValue() = ec.getIndex()
     )
     or
-    not exists(e.getValue().asInt()) and
+    not exists(Content::KnownElementContent ec | ec.getIndex() = e.getValue()) and
     c.isAnyElement()
   )
   or
@@ -931,7 +937,7 @@ predicate storeStep(Node node1, ContentSet c, Node node2) {
     e = node1.asExpr() and
     not arrayExprStore(node1, _, _, e) and
     node2.asExpr().(CfgNodes::ExprNodes::ArrayLiteralCfgNode).getExpr(index) = e and
-    c.isKnownOrUnknownElement(ec) and
+    c.isKnownOrUnknownPositional(ec) and
     index = ec.getIndex().asInt()
   )
   or
@@ -939,32 +945,32 @@ predicate storeStep(Node node1, ContentSet c, Node node2) {
     node2.asExpr().(CfgNodes::ExprNodes::HashTableExprCfgNode).getValueFromKey(key) = node1.asExpr()
   |
     exists(Content::KnownElementContent ec |
-      c.isKnownOrUnknownElement(ec) and
-      ec.getIndex() = key.getValue()
+      c.isKnownOrUnknownKeyContent(ec) and
+      key.getValue() = ec.getIndex()
     )
     or
-    not exists(key.getValue()) and
-    c.isAnyElement()
+    not exists(Content::KnownKeyContent ec | ec.getIndex() = key.getValue()) and
+    c.isUnknownKeyContent()
   )
   or
   arrayExprStore(node1, c, node2, _)
   or
-  c.isAnyElement() and
+  c.isUnknownPositionalContent() and
   exists(CfgNode cfgNode |
     node1 = TPreReturnNodeImpl(cfgNode, false) and
     node2.(ReturnNodeImpl).getCfgScope() = cfgNode.getScope()
   )
   or
-  c.isAnyElement() and
+  c.isUnknownPositionalContent() and
   exists(CfgNode cfgNode |
     node1 = TImplicitWrapNode(cfgNode, true) and
     node2.(ReturnNodeImpl).getCfgScope() = cfgNode.getScope()
   )
   or
-  c.isAnyElement() and
-  exists(CfgNodes::ExprNodes::PipelineArgumentCfgNode arg |
-    node1 = TPrePipelineArgumentNode(arg) and
-    node2 = TPipelineArgumentNode(arg)
+  c.isUnknownPositionalContent() and
+  exists(CfgNodes::ProcessBlockCfgNode process |
+    node1 = TPreProcessNode(process) and
+    node2 = TProcessNode(process)
   )
   or
   FlowSummaryImpl::Private::Steps::summaryStoreStep(node1.(FlowSummaryNode).getSummaryNode(), c,
@@ -992,7 +998,7 @@ predicate readStep(Node node1, ContentSet c, Node node2) {
       e.getValue() = ec.getIndex()
     )
     or
-    not exists(e.getValue()) and
+    not exists(Content::KnownElementContent ec | ec.getIndex() = e.getValue()) and
     c.isAnyElement()
   )
   or
@@ -1002,27 +1008,24 @@ predicate readStep(Node node1, ContentSet c, Node node2) {
     c.isSingleton(any(Content::KnownElementContent ec | exists(ec.getIndex().asInt())))
   )
   or
-  c.isAnyElement() and
+  c.isAnyPositional() and
   exists(CfgNodes::ProcessBlockCfgNode processBlock |
     processBlock.getPipelineVariableAccess() = node1.asExpr() and
     node2 = TProcessNode(processBlock)
   )
   or
-  exists(
-    Content::KnownElementContent ec, PipelineByPropertyNameParameter p, SsaImpl::DefinitionExt def
-  |
-    c.isSingleton(ec) and
-    p.getIteratorVariable() = node1.(ProcessPropertyByNameNode).getVariable() and
-    p.getName() = ec.getIndex().asString() and
-    def.getSourceVariable() = p.getIteratorVariable() and
-    SsaImpl::firstRead(def, node2.asExpr())
+  c.isAnyPositional() and
+  exists(CfgNodes::ProcessBlockCfgNode pb, CfgNodes::ExprNodes::VarReadAccessCfgNode va |
+    va = pb.getAPipelineByPropertyNameParameterAccess() and
+    node1.asExpr() = va and
+    node2 = TProcessPropertyByNameNode(va.getVariable(), false)
   )
   or
-  exists(Content::KnownElementContent ec, SsaImpl::DefinitionExt def |
-    c.isSingleton(ec) and
-    node1.(PipelineByPropertyNameParameterNode).getPropertyName() = ec.getIndex().asString() and
-    def = SsaImpl::getParameterDef(node1.(PipelineByPropertyNameParameterNode).getParameter()) and
-    SsaImpl::firstRead(def, node2.asExpr())
+  exists(PipelineByPropertyNameParameter p, Content::KnownElementContent ec |
+    c.isKnownOrUnknownElement(ec) and
+    ec.getIndex().asString() = p.getPropertyName() and
+    node1 = TProcessPropertyByNameNode(p, false) and
+    node2 = TProcessPropertyByNameNode(p, true)
   )
   or
   FlowSummaryImpl::Private::Steps::summaryReadStep(node1.(FlowSummaryNode).getSummaryNode(), c,
@@ -1043,8 +1046,11 @@ predicate clearsContent(Node n, ContentSet c) {
   n = TPreReturnNodeImpl(_, false) and
   c.isAnyElement()
   or
-  n instanceof PrePipelineArgumentNodeImpl and
-  c.isAnyElement()
+  c.isAnyPositional() and
+  n instanceof PreProcessPropertyByNameNode
+  or
+  c.isAnyPositional() and
+  n instanceof PreProcessNode
 }
 
 /**
@@ -1059,9 +1065,6 @@ predicate expectsContent(Node n, ContentSet c) {
   or
   n = TImplicitWrapNode(_, false) and
   c.isSingleton(any(Content::UnknownElementContent ec))
-  or
-  n instanceof PipelineArgumentNode and
-  c.isAnyElement()
 }
 
 class DataFlowType extends TDataFlowType {
@@ -1191,6 +1194,22 @@ private class ReturnNodeImpl extends TReturnNodeImpl, NodeImpl {
   override predicate nodeIsHidden() { any() }
 }
 
+private class PreProcessNode extends TPreProcessNode, NodeImpl {
+  CfgNodes::ProcessBlockCfgNode process;
+
+  PreProcessNode() { this = TPreProcessNode(process) }
+
+  override CfgScope getCfgScope() { result = process.getScope() }
+
+  override Location getLocationImpl() { result = process.getLocation() }
+
+  override string toStringImpl() { result = "pre-process node for " + process.toString() }
+
+  override predicate nodeIsHidden() { any() }
+
+  CfgNodes::ProcessBlockCfgNode getProcessBlock() { result = process }
+}
+
 private class ProcessNode extends TProcessNode, NodeImpl {
   CfgNodes::ProcessBlockCfgNode process;
 
@@ -1211,26 +1230,53 @@ private class ProcessNode extends TProcessNode, NodeImpl {
   CfgNodes::ProcessBlockCfgNode getProcessBlock() { result = process }
 }
 
-private class ProcessPropertyByNameNode extends TProcessPropertyByNameNode, NodeImpl {
-  private PipelineByPropertyNameIteratorVariable iter;
+private class PreProcessPropertyByNameNode extends TPreProcessPropertyByNameNode, NodeImpl {
+  private CfgNodes::ExprNodes::VarReadAccessCfgNode va;
 
-  ProcessPropertyByNameNode() { this = TProcessPropertyByNameNode(iter) }
+  PreProcessPropertyByNameNode() { this = TPreProcessPropertyByNameNode(va) }
 
-  PipelineByPropertyNameIteratorVariable getVariable() { result = iter }
+  CfgNodes::ExprNodes::VarReadAccessCfgNode getAccess() { result = va }
 
-  override CfgScope getCfgScope() { result = iter.getDeclaringScope() }
+  override CfgScope getCfgScope() { result = va.getScope() }
 
-  override Location getLocationImpl() { result = iter.getLocation() }
+  override Location getLocationImpl() { result = this.getProcessBlock().getLocation() }
 
-  override string toStringImpl() { result = "process node for " + iter.toString() }
+  override string toStringImpl() { result = "pre-process node for " + va.toString() }
 
   override predicate nodeIsHidden() { any() }
 
   CfgNodes::ProcessBlockCfgNode getProcessBlock() {
-    isProcessPropertyByNameNode(iter, result.getAstNode())
+    result.getAPipelineByPropertyNameParameterAccess() = va
   }
 }
 
+private class ProcessPropertyByNameNode extends TProcessPropertyByNameNode, NodeImpl {
+  private PipelineByPropertyNameParameter p;
+  private boolean hasRead;
+
+  ProcessPropertyByNameNode() { this = TProcessPropertyByNameNode(p, hasRead) }
+
+  PipelineByPropertyNameParameter getParameter() { result = p }
+
+  override CfgScope getCfgScope() { result = p.getDeclaringScope() }
+
+  override Location getLocationImpl() { result = this.getProcessBlock().getLocation() }
+
+  override string toStringImpl() {
+    hasRead = false and
+    result = "process node for " + p.toString()
+    or
+    hasRead = true and
+    result = "[has read] process node for " + p.toString()
+  }
+
+  override predicate nodeIsHidden() { any() }
+
+  CfgNodes::ProcessBlockCfgNode getProcessBlock() { result.getScope().getAParameter() = p }
+
+  predicate hasRead() { hasRead = true }
+}
+
 class ScriptBlockNode extends TScriptBlockNode, NodeImpl {
   private ScriptBlock scriptBlock;
 
@@ -1338,18 +1384,38 @@ class ContentApprox extends TContentApprox {
 
 /** Gets an approximated value for content `c`. */
 ContentApprox getContentApprox(Content c) {
-  c instanceof Content::UnknownElementContent and
-  result = TUnknownElementContentApprox()
+  c instanceof Content::KnownPositionalContent and
+  result = TKnownPositionalContentApprox()
   or
-  exists(c.(Content::KnownElementContent).getIndex().asInt()) and
-  result = TKnownIntegerElementContentApprox()
-  or
-  result =
-    TKnownElementContentApprox(approxKnownElementIndex(c.(Content::KnownElementContent).getIndex()))
+  result = TKnownKeyContentApprox(approxKnownElementIndex(c.(Content::KnownKeyContent).getIndex()))
   or
   result = TNonElementContentApprox(c)
+  or
+  c instanceof Content::UnknownKeyContent and
+  result = TUnkownKeyContentApprox()
+  or
+  c instanceof Content::UnknownPositionalContent and
+  result = TUnknownPositionalContentApprox()
+  or
+  c instanceof Content::UnknownKeyOrPositionContent and
+  result = TUnknownContentApprox()
 }
 
+// TFieldContent(string name) {
+//   name = any(PropertyMember member).getName()
+//   or
+//   name = any(MemberExpr me).getMemberName()
+// } or
+// // A known map key
+// TKnownKeyContent(ConstantValue cv) { exists(cv.asString()) } or
+// // A known array index
+// TKnownPositionalContent(ConstantValue cv) { cv.asInt() = [0 .. 10] } or
+// // An unknown key
+// TUnknownKeyContent() or
+// // An unknown positional element
+// TUnknownPositionalContent() or
+// // A unknown position or key - and we dont even know what kind it is
+// TUnknownKeyOrPositionContent()
 /**
  * A unit class for adding additional jump steps.
  *
diff --git a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPublic.qll b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPublic.qll
index 7848fb6e2a7d..28cfd4ed3040 100644
--- a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPublic.qll
+++ b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPublic.qll
@@ -255,21 +255,43 @@ module Content {
   /** An element in a collection, for example an element in an array or in a hash. */
   class ElementContent extends Content, TElementContent { }
 
-  /** An element in a collection at a known index. */
-  class KnownElementContent extends ElementContent, TKnownElementContent {
-    private ConstantValue cv;
-
-    KnownElementContent() { this = TKnownElementContent(cv) }
+  abstract class KnownElementContent extends ElementContent, TKnownElementContent {
+    ConstantValue cv;
 
     /** Gets the index in the collection. */
-    ConstantValue getIndex() { result = cv }
+    final ConstantValue getIndex() { result = cv }
 
     override string toString() { result = "element " + cv }
   }
 
-  /** An element in a collection at an unknown index. */
-  class UnknownElementContent extends ElementContent, TUnknownElementContent {
-    override string toString() { result = "element" }
+  /** An element in a collection at a known index. */
+  class KnownKeyContent extends KnownElementContent, TKnownKeyContent {
+    KnownKeyContent() { this = TKnownKeyContent(cv) }
+  }
+
+  /** An element in a collection at a known index. */
+  class KnownPositionalContent extends KnownElementContent, TKnownPositionalContent {
+    KnownPositionalContent() { this = TKnownPositionalContent(cv) }
+  }
+
+  class UnknownElementContent extends ElementContent, TUnknownElementContent { }
+
+  class UnknownKeyContent extends UnknownElementContent, TUnknownKeyContent {
+    UnknownKeyContent() { this = TUnknownKeyContent() }
+
+    override string toString() { result = "unknown map key" }
+  }
+
+  class UnknownPositionalContent extends UnknownElementContent, TUnknownPositionalContent {
+    UnknownPositionalContent() { this = TUnknownPositionalContent() }
+
+    override string toString() { result = "unknown index" }
+  }
+
+  class UnknownKeyOrPositionContent extends UnknownElementContent, TUnknownKeyOrPositionContent {
+    UnknownKeyOrPositionContent() { this = TUnknownKeyOrPositionContent() }
+
+    override string toString() { result = "unknown" }
   }
 
   /** A field of an object. */
@@ -285,20 +307,18 @@ module Content {
   }
 
   /** Gets the element content corresponding to constant value `cv`. */
-  ElementContent getElementContent(ConstantValue cv) {
-    result = TKnownElementContent(cv)
+  KnownElementContent getKnownElementContent(ConstantValue cv) {
+    result = TKnownPositionalContent(cv)
     or
-    not exists(TKnownElementContent(cv)) and
-    result = TUnknownElementContent()
+    result = TKnownKeyContent(cv)
   }
 
   /**
    * Gets the constant value of `e`, which corresponds to a valid known
-   * element index. Unlike calling simply `e.getConstantValue()`, this
-   * excludes negative array indices.
+   * element index.
    */
   ConstantValue getKnownElementIndex(Expr e) {
-    result = getElementContent(e.getValue()).(KnownElementContent).getIndex()
+    result = getKnownElementContent(e.getValue()).getIndex()
   }
 }
 
@@ -310,19 +330,31 @@ module Content {
  */
 class ContentSet extends TContentSet {
   /** Holds if this content set is the singleton `{c}`. */
-  predicate isSingleton(Content c) { this = TSingletonContent(c) }
+  predicate isSingleton(Content c) { this = TSingletonContentSet(c) }
 
-  /** Holds if this content set represents all `ElementContent`s. */
-  predicate isAnyElement() { this = TAnyElementContent() }
+  predicate isKnownOrUnknownKeyContent(Content::KnownKeyContent c) {
+    this = TKnownOrUnknownKeyContentSet(c)
+  }
+
+  predicate isKnownOrUnknownPositional(Content::KnownPositionalContent c) {
+    this = TKnownOrUnknownPositionalContentSet(c)
+  }
 
-  /**
-   * Holds if this content set represents a specific known element index, or an
-   * unknown element index.
-   */
   predicate isKnownOrUnknownElement(Content::KnownElementContent c) {
-    this = TKnownOrUnknownElementContent(c)
+    this.isKnownOrUnknownKeyContent(c)
+    or
+    this.isKnownOrUnknownPositional(c)
   }
 
+  predicate isUnknownPositionalContent() { this = TUnknownPositionalElementContentSet() }
+
+  predicate isUnknownKeyContent() { this = TUnknownKeyContentSet() }
+
+  predicate isAnyElement() { this = TAnyElementContentSet() }
+
+  predicate isAnyPositional() { this = TAnyPositionalContentSet() }
+
+  // predicate isPipelineContentSet() { this = TPipelineContentSet() }
   /** Gets a textual representation of this content set. */
   string toString() {
     exists(Content c |
@@ -330,15 +362,25 @@ class ContentSet extends TContentSet {
       result = c.toString()
     )
     or
-    this.isAnyElement() and
-    result = "any element"
-    or
     exists(Content::KnownElementContent c |
       this.isKnownOrUnknownElement(c) and
-      result = c + " or unknown"
+      result = c.toString() + " or unknown"
     )
+    or
+    this.isUnknownPositionalContent() and
+    result = "unknown positional"
+    or
+    this.isUnknownKeyContent() and
+    result = "unknown key"
+    or
+    this.isAnyPositional() and
+    result = "any positional"
+    or
+    this.isAnyElement() and
+    result = "any element"
   }
 
+  /** Gets a content that may be stored into when storing into this set. */
   Content getAStoreContent() {
     this.isSingleton(result)
     or
@@ -346,20 +388,25 @@ class ContentSet extends TContentSet {
     // from `a` to `a[unknown]` (which can read any element), gets translated into
     // a reverse store step that store only into `?`
     this.isAnyElement() and
-    result = TUnknownElementContent()
+    result = TUnknownKeyOrPositionContent()
     or
     // For reverse stores, `a[1][0] = x`, it is important that the read-step
     // from `a` to `a[1]` (which can read both elements stored at exactly index `1`
     // and elements stored at unknown index), gets translated into a reverse store
     // step that store only into `1`
     this.isKnownOrUnknownElement(result)
-  }
-
-  pragma[nomagic]
-  private Content getAnElementReadContent() {
-    exists(Content::KnownElementContent c | this.isKnownOrUnknownElement(c) |
-      result = c or
-      result = TUnknownElementContent()
+    or
+    this.isUnknownPositionalContent() and
+    result = TUnknownPositionalContent()
+    or
+    this.isUnknownKeyContent() and
+    result = TUnknownKeyContent()
+    or
+    this.isAnyPositional() and
+    (
+      result instanceof Content::KnownPositionalContent
+      or
+      result = TUnknownPositionalContent()
     )
   }
 
@@ -370,7 +417,36 @@ class ContentSet extends TContentSet {
     this.isAnyElement() and
     result instanceof Content::ElementContent
     or
-    result = this.getAnElementReadContent()
+    exists(Content::KnownElementContent c |
+      this.isKnownOrUnknownKeyContent(c) and
+      (
+        result = c
+        or
+        result = TUnknownKeyContent()
+        or
+        result = TUnknownKeyOrPositionContent()
+      )
+      or
+      this.isKnownOrUnknownPositional(c) and
+      (
+        result = c or
+        result = TUnknownPositionalContent() or
+        result = TUnknownKeyOrPositionContent()
+      )
+    )
+    or
+    this.isUnknownPositionalContent() and
+    result = TUnknownPositionalContent()
+    or
+    this.isUnknownKeyContent() and
+    result = TUnknownKeyContent()
+    or
+    this.isAnyPositional() and
+    (
+      result instanceof Content::KnownPositionalContent
+      or
+      result = TUnknownPositionalContent()
+    )
   }
 }
 
diff --git a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/FlowSummaryImpl.qll b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/FlowSummaryImpl.qll
index b5f8d7beeacd..93cffe4a250b 100644
--- a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/FlowSummaryImpl.qll
+++ b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/FlowSummaryImpl.qll
@@ -52,22 +52,24 @@ module Input implements InputSig<Location, DataFlowImplSpecific::PowershellDataF
   }
 
   string encodeContent(ContentSet cs, string arg) {
-    exists(Content c | cs = TSingletonContent(c) |
+    exists(Content c | cs = TSingletonContentSet(c) |
       c = TFieldContent(arg) and result = "Field"
       or
-      exists(ConstantValue cv |
-        c = TKnownElementContent(cv) and
+      exists(ConstantValue cv | c = TKnownKeyContent(cv) or c = TKnownPositionalContent(cv) |
         result = "Element" and
         arg = cv.serialize() + "!"
       )
       or
-      c = TUnknownElementContent() and result = "Element" and arg = "?"
+      (c = TUnknownPositionalContent() or c = TUnknownKeyContent()) and
+      result = "Element" and
+      arg = "?"
     )
     or
-    cs = TAnyElementContent() and result = "Element" and arg = "any"
+    cs = TAnyElementContentSet() and result = "Element" and arg = "any"
     or
     exists(Content::KnownElementContent kec |
-      cs = TKnownOrUnknownElementContent(kec) and
+      cs = TKnownOrUnknownKeyContentSet(kec) or cs = TKnownOrUnknownPositionalContentSet(kec)
+    |
       result = "Element" and
       arg = kec.getIndex().serialize()
     )
@@ -102,13 +104,13 @@ module Input implements InputSig<Location, DataFlowImplSpecific::PowershellDataF
   bindingset[token]
   ContentSet decodeUnknownContent(AccessPath::AccessPathTokenBase token) {
     token.getName() = "Element" and
-    result = TSingletonContent(TUnknownElementContent())
+    result = TSingletonContentSet(TUnknownKeyOrPositionContent())
   }
 
   bindingset[token]
   ContentSet decodeUnknownWithContent(AccessPath::AccessPathTokenBase token) {
     token.getName() = "WithElement" and
-    result = TAnyElementContent()
+    result = TAnyElementContentSet()
   }
 }
 
@@ -152,12 +154,12 @@ module Private {
 
     /** Gets a summary component that represents an element in a collection at an unknown index. */
     SummaryComponent elementUnknown() {
-      result = SC::content(TSingletonContent(TUnknownElementContent()))
+      result = SC::content(TSingletonContentSet(TUnknownKeyOrPositionContent()))
     }
 
     /** Gets a summary component that represents an element in a collection at a known index. */
     SummaryComponent elementKnown(ConstantValue cv) {
-      result = SC::content(TSingletonContent(Content::getElementContent(cv)))
+      result = SC::content(TSingletonContentSet(Content::getKnownElementContent(cv)))
     }
 
     /**
@@ -165,9 +167,14 @@ module Private {
      * known index `cv`, or an unknown index.
      */
     SummaryComponent elementKnownOrUnknown(ConstantValue cv) {
-      result = SC::content(TKnownOrUnknownElementContent(TKnownElementContent(cv)))
+      result =
+        SC::content(any(ContentSet cs |
+            cs.isKnownOrUnknownElement(Content::getKnownElementContent(cv))
+          ))
       or
-      not exists(TKnownElementContent(cv)) and
+      not exists(
+        any(ContentSet cs | cs.isKnownOrUnknownElement(Content::getKnownElementContent(cv)))
+      ) and
       result = elementUnknown()
     }
 
@@ -181,7 +188,7 @@ module Private {
      *
      * but is more efficient, because it is represented by a single value.
      */
-    SummaryComponent elementAny() { result = SC::content(TAnyElementContent()) }
+    SummaryComponent elementAny() { result = SC::content(TAnyElementContentSet()) }
 
     /** Gets a summary component that represents the return value of a call. */
     SummaryComponent return() { result = SC::return(any(NormalReturnKind rk)) }
diff --git a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/SsaImpl.qll b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/SsaImpl.qll
index 507ebe7f849a..44130ae12661 100644
--- a/powershell/ql/lib/semmle/code/powershell/dataflow/internal/SsaImpl.qll
+++ b/powershell/ql/lib/semmle/code/powershell/dataflow/internal/SsaImpl.qll
@@ -31,9 +31,10 @@ module SsaInput implements SsaImplCommon::InputSig<Location> {
       or
       variableWriteActual(bb, i, v, _)
       or
-      exists(ProcessBlockCfgNode processBlock |
-        bb.getNode(i) = processBlock and
+      exists(ProcessBlockCfgNode processBlock | bb.getNode(i) = processBlock |
         processBlock.getPipelineIteratorVariable() = v
+        or
+        processBlock.getAPipelineBypropertyNameIteratorVariable() = v
       )
       or
       parameterWrite(bb, i, v)
@@ -301,7 +302,8 @@ class NormalParameter extends Parameter {
 private newtype TParameterExt =
   TNormalParameter(NormalParameter p) or
   TThisMethodParameter(Method m) or
-  TPipelineParameter(PipelineParameter p)
+  TPipelineParameter(PipelineParameter p) or
+  TPipelineByPropertyNameParameter(PipelineByPropertyNameParameter p)
 
 /** A normal parameter or an implicit `this` parameter. */
 class ParameterExt extends TParameterExt {
@@ -311,11 +313,17 @@ class ParameterExt extends TParameterExt {
 
   PipelineParameter asPipelineParameter() { this = TPipelineParameter(result) }
 
+  PipelineByPropertyNameParameter asPipelineByPropertyNameParameter() {
+    this = TPipelineByPropertyNameParameter(result)
+  }
+
   predicate isInitializedBy(WriteDefinition def) {
     def = getParameterDef(this.asParameter())
     or
     def = getParameterDef(this.asPipelineParameter())
     or
+    def = getParameterDef(this.asPipelineByPropertyNameParameter())
+    or
     def.(Ssa::ThisDefinition).getSourceVariable().getDeclaringScope() = this.asThis().getBody()
   }
 
@@ -323,7 +331,7 @@ class ParameterExt extends TParameterExt {
     result =
       [
         this.asParameter().toString(), this.asThis().toString(),
-        this.asPipelineParameter().toString()
+        this.asPipelineParameter().toString(), this.asPipelineByPropertyNameParameter().toString()
       ]
   }
 
@@ -331,7 +339,8 @@ class ParameterExt extends TParameterExt {
     result =
       [
         this.asParameter().getLocation(), this.asThis().getLocation(),
-        this.asPipelineParameter().getLocation()
+        this.asPipelineParameter().getLocation(),
+        this.asPipelineByPropertyNameParameter().getLocation()
       ]
   }
 }
diff --git a/powershell/ql/test/library-tests/controlflow/graph/Cfg.expected b/powershell/ql/test/library-tests/controlflow/graph/Cfg.expected
index ea88eea58ae6..51cfda6735d2 100644
--- a/powershell/ql/test/library-tests/controlflow/graph/Cfg.expected
+++ b/powershell/ql/test/library-tests/controlflow/graph/Cfg.expected
@@ -271,8 +271,14 @@
 | functions.ps1:28:5:28:8 | sum | functions.ps1:28:12:28:12 | 0 |  |
 | functions.ps1:28:5:28:12 | ...=... | functions.ps1:28:5:28:8 | sum |  |
 | functions.ps1:28:12:28:12 | 0 | functions.ps1:29:25:29:32 | numbers |  |
+| functions.ps1:29:5:32:5 | forach(... in ...) | functions.ps1:29:14:29:20 | number | non-empty |
 | functions.ps1:29:5:32:5 | forach(... in ...) | functions.ps1:33:5:33:8 | [Stmt] sum | empty |
+| functions.ps1:29:14:29:20 | number | functions.ps1:29:35:32:5 | {...} |  |
 | functions.ps1:29:25:29:32 | numbers | functions.ps1:29:5:32:5 | forach(... in ...) |  |
+| functions.ps1:29:35:32:5 | {...} | functions.ps1:31:9:31:23 | ...=... |  |
+| functions.ps1:31:9:31:12 | sum | functions.ps1:31:17:31:23 | number |  |
+| functions.ps1:31:9:31:23 | ...=... | functions.ps1:31:9:31:12 | sum |  |
+| functions.ps1:31:17:31:23 | number | functions.ps1:29:5:32:5 | forach(... in ...) |  |
 | functions.ps1:33:5:33:8 | [Stmt] sum | functions.ps1:33:5:33:8 | sum |  |
 | functions.ps1:33:5:33:8 | sum | functions.ps1:22:33:34:1 | exit {...} (normal) |  |
 | functions.ps1:36:1:52:1 | def of Add-Numbers-From-Pipeline | functions.ps1:1:1:54:0 | exit {...} (normal) |  |
@@ -284,9 +290,10 @@
 | functions.ps1:41:5:43:5 | {...} | functions.ps1:42:9:42:16 | ...=... |  |
 | functions.ps1:42:9:42:12 | sum | functions.ps1:42:16:42:16 | 0 |  |
 | functions.ps1:42:9:42:16 | ...=... | functions.ps1:42:9:42:12 | sum |  |
-| functions.ps1:42:16:42:16 | 0 | functions.ps1:44:5:47:5 | [synth] pipeline |  |
-| functions.ps1:44:5:47:5 | [synth] pipeline | functions.ps1:44:5:47:5 | {...} |  |
-| functions.ps1:44:5:47:5 | {...} | functions.ps1:46:9:46:18 | ...=... |  |
+| functions.ps1:42:16:42:16 | 0 | functions.ps1:44:5:47:5 | {...} |  |
+| functions.ps1:44:5:47:5 | [synth] pipeline | functions.ps1:46:9:46:18 | ...=... | non-empty |
+| functions.ps1:44:5:47:5 | [synth] pipeline | functions.ps1:48:5:51:5 | {...} | empty |
+| functions.ps1:44:5:47:5 | {...} | functions.ps1:44:5:47:5 | [synth] pipeline |  |
 | functions.ps1:46:9:46:12 | sum | functions.ps1:46:17:46:18 | __pipeline_iterator |  |
 | functions.ps1:46:9:46:18 | ...=... | functions.ps1:46:9:46:12 | sum |  |
 | functions.ps1:46:17:46:18 | __pipeline_iterator | functions.ps1:44:5:47:5 | [synth] pipeline |  |
@@ -452,7 +459,15 @@
 | loops.ps1:51:5:51:10 | ...=... | loops.ps1:51:5:51:6 | a |  |
 | loops.ps1:51:10:51:10 | 0 | loops.ps1:52:25:52:36 | letterArray |  |
 | loops.ps1:52:5:55:5 | forach(... in ...) | loops.ps1:49:23:56:1 | exit {...} (normal) | empty |
+| loops.ps1:52:5:55:5 | forach(... in ...) | loops.ps1:52:14:52:20 | letter | non-empty |
+| loops.ps1:52:14:52:20 | letter | loops.ps1:53:5:55:5 | {...} |  |
 | loops.ps1:52:25:52:36 | letterArray | loops.ps1:52:5:55:5 | forach(... in ...) |  |
+| loops.ps1:53:5:55:5 | {...} | loops.ps1:54:9:54:19 | ...=... |  |
+| loops.ps1:54:9:54:10 | a | loops.ps1:54:14:54:15 | a |  |
+| loops.ps1:54:9:54:19 | ...=... | loops.ps1:54:9:54:10 | a |  |
+| loops.ps1:54:14:54:15 | a | loops.ps1:54:19:54:19 | 1 |  |
+| loops.ps1:54:14:54:19 | ...+... | loops.ps1:52:5:55:5 | forach(... in ...) |  |
+| loops.ps1:54:19:54:19 | 1 | loops.ps1:54:14:54:19 | ...+... |  |
 | loops.ps1:58:1:68:1 | def of Test-For-Ever | loops.ps1:1:1:70:0 | exit {...} (normal) |  |
 | loops.ps1:58:24:68:1 | [synth] pipeline | loops.ps1:59:5:67:5 | {...} |  |
 | loops.ps1:58:24:68:1 | enter {...} | loops.ps1:58:24:68:1 | {...} |  |
diff --git a/powershell/ql/test/library-tests/dataflow/fields/test.expected b/powershell/ql/test/library-tests/dataflow/fields/test.expected
index 0908f093abc0..0f9350477142 100644
--- a/powershell/ql/test/library-tests/dataflow/fields/test.expected
+++ b/powershell/ql/test/library-tests/dataflow/fields/test.expected
@@ -6,33 +6,33 @@ edges
 | test.ps1:10:1:10:5 | [post] arr1 [element 3] | test.ps1:11:6:11:10 | arr1 [element 3] | provenance |  |
 | test.ps1:10:12:10:21 | Call to Source | test.ps1:10:1:10:5 | [post] arr1 [element 3] | provenance |  |
 | test.ps1:11:6:11:10 | arr1 [element 3] | test.ps1:11:6:11:13 | ...[...] | provenance |  |
-| test.ps1:14:1:14:5 | [post] arr2 [element] | test.ps1:15:6:15:10 | arr2 [element] | provenance |  |
-| test.ps1:14:19:14:28 | Call to Source | test.ps1:14:1:14:5 | [post] arr2 [element] | provenance |  |
-| test.ps1:15:6:15:10 | arr2 [element] | test.ps1:15:6:15:13 | ...[...] | provenance |  |
+| test.ps1:14:1:14:5 | [post] arr2 [unknown] | test.ps1:15:6:15:10 | arr2 [unknown] | provenance |  |
+| test.ps1:14:19:14:28 | Call to Source | test.ps1:14:1:14:5 | [post] arr2 [unknown] | provenance |  |
+| test.ps1:15:6:15:10 | arr2 [unknown] | test.ps1:15:6:15:13 | ...[...] | provenance |  |
 | test.ps1:17:1:17:5 | [post] arr3 [element 3] | test.ps1:18:6:18:10 | arr3 [element 3] | provenance |  |
 | test.ps1:17:12:17:21 | Call to Source | test.ps1:17:1:17:5 | [post] arr3 [element 3] | provenance |  |
 | test.ps1:18:6:18:10 | arr3 [element 3] | test.ps1:18:6:18:20 | ...[...] | provenance |  |
-| test.ps1:20:1:20:5 | [post] arr4 [element] | test.ps1:21:6:21:10 | arr4 [element] | provenance |  |
-| test.ps1:20:20:20:29 | Call to Source | test.ps1:20:1:20:5 | [post] arr4 [element] | provenance |  |
-| test.ps1:21:6:21:10 | arr4 [element] | test.ps1:21:6:21:21 | ...[...] | provenance |  |
-| test.ps1:23:1:23:5 | [post] arr5 [element, element 1] | test.ps1:24:6:24:10 | arr5 [element, element 1] | provenance |  |
-| test.ps1:23:1:23:16 | [post] ...[...] [element 1] | test.ps1:23:1:23:5 | [post] arr5 [element, element 1] | provenance |  |
+| test.ps1:20:1:20:5 | [post] arr4 [unknown] | test.ps1:21:6:21:10 | arr4 [unknown] | provenance |  |
+| test.ps1:20:20:20:29 | Call to Source | test.ps1:20:1:20:5 | [post] arr4 [unknown] | provenance |  |
+| test.ps1:21:6:21:10 | arr4 [unknown] | test.ps1:21:6:21:21 | ...[...] | provenance |  |
+| test.ps1:23:1:23:5 | [post] arr5 [unknown, element 1] | test.ps1:24:6:24:10 | arr5 [unknown, element 1] | provenance |  |
+| test.ps1:23:1:23:16 | [post] ...[...] [element 1] | test.ps1:23:1:23:5 | [post] arr5 [unknown, element 1] | provenance |  |
 | test.ps1:23:23:23:32 | Call to Source | test.ps1:23:1:23:16 | [post] ...[...] [element 1] | provenance |  |
-| test.ps1:24:6:24:10 | arr5 [element, element 1] | test.ps1:24:6:24:21 | ...[...] [element 1] | provenance |  |
+| test.ps1:24:6:24:10 | arr5 [unknown, element 1] | test.ps1:24:6:24:21 | ...[...] [element 1] | provenance |  |
 | test.ps1:24:6:24:21 | ...[...] [element 1] | test.ps1:24:6:24:24 | ...[...] | provenance |  |
-| test.ps1:27:1:27:5 | [post] arr6 [element 1, element] | test.ps1:28:6:28:10 | arr6 [element 1, element] | provenance |  |
-| test.ps1:27:1:27:8 | [post] ...[...] [element] | test.ps1:27:1:27:5 | [post] arr6 [element 1, element] | provenance |  |
-| test.ps1:27:23:27:32 | Call to Source | test.ps1:27:1:27:8 | [post] ...[...] [element] | provenance |  |
-| test.ps1:28:6:28:10 | arr6 [element 1, element] | test.ps1:28:6:28:13 | ...[...] [element] | provenance |  |
-| test.ps1:28:6:28:13 | ...[...] [element] | test.ps1:28:6:28:24 | ...[...] | provenance |  |
-| test.ps1:31:1:31:5 | [post] arr7 [element, element] | test.ps1:32:6:32:10 | arr7 [element, element] | provenance |  |
-| test.ps1:31:1:31:5 | [post] arr7 [element, element] | test.ps1:33:6:33:10 | arr7 [element, element] | provenance |  |
-| test.ps1:31:1:31:16 | [post] ...[...] [element] | test.ps1:31:1:31:5 | [post] arr7 [element, element] | provenance |  |
-| test.ps1:31:31:31:40 | Call to Source | test.ps1:31:1:31:16 | [post] ...[...] [element] | provenance |  |
-| test.ps1:32:6:32:10 | arr7 [element, element] | test.ps1:32:6:32:13 | ...[...] [element] | provenance |  |
-| test.ps1:32:6:32:13 | ...[...] [element] | test.ps1:32:6:32:16 | ...[...] | provenance |  |
-| test.ps1:33:6:33:10 | arr7 [element, element] | test.ps1:33:6:33:21 | ...[...] [element] | provenance |  |
-| test.ps1:33:6:33:21 | ...[...] [element] | test.ps1:33:6:33:32 | ...[...] | provenance |  |
+| test.ps1:27:1:27:5 | [post] arr6 [element 1, unknown] | test.ps1:28:6:28:10 | arr6 [element 1, unknown] | provenance |  |
+| test.ps1:27:1:27:8 | [post] ...[...] [unknown] | test.ps1:27:1:27:5 | [post] arr6 [element 1, unknown] | provenance |  |
+| test.ps1:27:23:27:32 | Call to Source | test.ps1:27:1:27:8 | [post] ...[...] [unknown] | provenance |  |
+| test.ps1:28:6:28:10 | arr6 [element 1, unknown] | test.ps1:28:6:28:13 | ...[...] [unknown] | provenance |  |
+| test.ps1:28:6:28:13 | ...[...] [unknown] | test.ps1:28:6:28:24 | ...[...] | provenance |  |
+| test.ps1:31:1:31:5 | [post] arr7 [unknown, unknown] | test.ps1:32:6:32:10 | arr7 [unknown, unknown] | provenance |  |
+| test.ps1:31:1:31:5 | [post] arr7 [unknown, unknown] | test.ps1:33:6:33:10 | arr7 [unknown, unknown] | provenance |  |
+| test.ps1:31:1:31:16 | [post] ...[...] [unknown] | test.ps1:31:1:31:5 | [post] arr7 [unknown, unknown] | provenance |  |
+| test.ps1:31:31:31:40 | Call to Source | test.ps1:31:1:31:16 | [post] ...[...] [unknown] | provenance |  |
+| test.ps1:32:6:32:10 | arr7 [unknown, unknown] | test.ps1:32:6:32:13 | ...[...] [unknown] | provenance |  |
+| test.ps1:32:6:32:13 | ...[...] [unknown] | test.ps1:32:6:32:16 | ...[...] | provenance |  |
+| test.ps1:33:6:33:10 | arr7 [unknown, unknown] | test.ps1:33:6:33:21 | ...[...] [unknown] | provenance |  |
+| test.ps1:33:6:33:21 | ...[...] [unknown] | test.ps1:33:6:33:32 | ...[...] | provenance |  |
 | test.ps1:35:6:35:16 | Call to Source | test.ps1:37:15:37:16 | x | provenance |  |
 | test.ps1:37:9:37:16 | ...,... [element 2] | test.ps1:40:6:40:10 | arr8 [element 2] | provenance |  |
 | test.ps1:37:9:37:16 | ...,... [element 2] | test.ps1:41:6:41:10 | arr8 [element 2] | provenance |  |
@@ -53,15 +53,15 @@ edges
 | test.ps1:66:10:66:20 | Call to Source | test.ps1:69:5:69:6 | x | provenance |  |
 | test.ps1:67:10:67:20 | Call to Source | test.ps1:70:5:70:6 | y | provenance |  |
 | test.ps1:68:10:68:20 | Call to Source | test.ps1:70:9:70:10 | z | provenance |  |
-| test.ps1:69:5:69:6 | x | test.ps1:73:6:73:12 | Call to produce [element] | provenance |  |
-| test.ps1:70:5:70:6 | y | test.ps1:73:6:73:12 | Call to produce [element] | provenance |  |
-| test.ps1:70:9:70:10 | z | test.ps1:73:6:73:12 | Call to produce [element] | provenance |  |
-| test.ps1:73:6:73:12 | Call to produce [element] | test.ps1:74:6:74:7 | x [element] | provenance |  |
-| test.ps1:73:6:73:12 | Call to produce [element] | test.ps1:75:6:75:7 | x [element] | provenance |  |
-| test.ps1:73:6:73:12 | Call to produce [element] | test.ps1:76:6:76:7 | x [element] | provenance |  |
-| test.ps1:74:6:74:7 | x [element] | test.ps1:74:6:74:10 | ...[...] | provenance |  |
-| test.ps1:75:6:75:7 | x [element] | test.ps1:75:6:75:10 | ...[...] | provenance |  |
-| test.ps1:76:6:76:7 | x [element] | test.ps1:76:6:76:10 | ...[...] | provenance |  |
+| test.ps1:69:5:69:6 | x | test.ps1:73:6:73:12 | Call to produce [unknown index] | provenance |  |
+| test.ps1:70:5:70:6 | y | test.ps1:73:6:73:12 | Call to produce [unknown index] | provenance |  |
+| test.ps1:70:9:70:10 | z | test.ps1:73:6:73:12 | Call to produce [unknown index] | provenance |  |
+| test.ps1:73:6:73:12 | Call to produce [unknown index] | test.ps1:74:6:74:7 | x [unknown index] | provenance |  |
+| test.ps1:73:6:73:12 | Call to produce [unknown index] | test.ps1:75:6:75:7 | x [unknown index] | provenance |  |
+| test.ps1:73:6:73:12 | Call to produce [unknown index] | test.ps1:76:6:76:7 | x [unknown index] | provenance |  |
+| test.ps1:74:6:74:7 | x [unknown index] | test.ps1:74:6:74:10 | ...[...] | provenance |  |
+| test.ps1:75:6:75:7 | x [unknown index] | test.ps1:75:6:75:10 | ...[...] | provenance |  |
+| test.ps1:76:6:76:7 | x [unknown index] | test.ps1:76:6:76:10 | ...[...] | provenance |  |
 | test.ps1:78:9:81:1 | ${...} [element a] | test.ps1:83:6:83:10 | hash [element a] | provenance |  |
 | test.ps1:78:9:81:1 | ${...} [element a] | test.ps1:87:6:87:10 | hash [element a] | provenance |  |
 | test.ps1:79:7:79:17 | Call to Source | test.ps1:78:9:81:1 | ${...} [element a] | provenance |  |
@@ -79,38 +79,38 @@ nodes
 | test.ps1:10:12:10:21 | Call to Source | semmle.label | Call to Source |
 | test.ps1:11:6:11:10 | arr1 [element 3] | semmle.label | arr1 [element 3] |
 | test.ps1:11:6:11:13 | ...[...] | semmle.label | ...[...] |
-| test.ps1:14:1:14:5 | [post] arr2 [element] | semmle.label | [post] arr2 [element] |
+| test.ps1:14:1:14:5 | [post] arr2 [unknown] | semmle.label | [post] arr2 [unknown] |
 | test.ps1:14:19:14:28 | Call to Source | semmle.label | Call to Source |
-| test.ps1:15:6:15:10 | arr2 [element] | semmle.label | arr2 [element] |
+| test.ps1:15:6:15:10 | arr2 [unknown] | semmle.label | arr2 [unknown] |
 | test.ps1:15:6:15:13 | ...[...] | semmle.label | ...[...] |
 | test.ps1:17:1:17:5 | [post] arr3 [element 3] | semmle.label | [post] arr3 [element 3] |
 | test.ps1:17:12:17:21 | Call to Source | semmle.label | Call to Source |
 | test.ps1:18:6:18:10 | arr3 [element 3] | semmle.label | arr3 [element 3] |
 | test.ps1:18:6:18:20 | ...[...] | semmle.label | ...[...] |
-| test.ps1:20:1:20:5 | [post] arr4 [element] | semmle.label | [post] arr4 [element] |
+| test.ps1:20:1:20:5 | [post] arr4 [unknown] | semmle.label | [post] arr4 [unknown] |
 | test.ps1:20:20:20:29 | Call to Source | semmle.label | Call to Source |
-| test.ps1:21:6:21:10 | arr4 [element] | semmle.label | arr4 [element] |
+| test.ps1:21:6:21:10 | arr4 [unknown] | semmle.label | arr4 [unknown] |
 | test.ps1:21:6:21:21 | ...[...] | semmle.label | ...[...] |
-| test.ps1:23:1:23:5 | [post] arr5 [element, element 1] | semmle.label | [post] arr5 [element, element 1] |
+| test.ps1:23:1:23:5 | [post] arr5 [unknown, element 1] | semmle.label | [post] arr5 [unknown, element 1] |
 | test.ps1:23:1:23:16 | [post] ...[...] [element 1] | semmle.label | [post] ...[...] [element 1] |
 | test.ps1:23:23:23:32 | Call to Source | semmle.label | Call to Source |
-| test.ps1:24:6:24:10 | arr5 [element, element 1] | semmle.label | arr5 [element, element 1] |
+| test.ps1:24:6:24:10 | arr5 [unknown, element 1] | semmle.label | arr5 [unknown, element 1] |
 | test.ps1:24:6:24:21 | ...[...] [element 1] | semmle.label | ...[...] [element 1] |
 | test.ps1:24:6:24:24 | ...[...] | semmle.label | ...[...] |
-| test.ps1:27:1:27:5 | [post] arr6 [element 1, element] | semmle.label | [post] arr6 [element 1, element] |
-| test.ps1:27:1:27:8 | [post] ...[...] [element] | semmle.label | [post] ...[...] [element] |
+| test.ps1:27:1:27:5 | [post] arr6 [element 1, unknown] | semmle.label | [post] arr6 [element 1, unknown] |
+| test.ps1:27:1:27:8 | [post] ...[...] [unknown] | semmle.label | [post] ...[...] [unknown] |
 | test.ps1:27:23:27:32 | Call to Source | semmle.label | Call to Source |
-| test.ps1:28:6:28:10 | arr6 [element 1, element] | semmle.label | arr6 [element 1, element] |
-| test.ps1:28:6:28:13 | ...[...] [element] | semmle.label | ...[...] [element] |
+| test.ps1:28:6:28:10 | arr6 [element 1, unknown] | semmle.label | arr6 [element 1, unknown] |
+| test.ps1:28:6:28:13 | ...[...] [unknown] | semmle.label | ...[...] [unknown] |
 | test.ps1:28:6:28:24 | ...[...] | semmle.label | ...[...] |
-| test.ps1:31:1:31:5 | [post] arr7 [element, element] | semmle.label | [post] arr7 [element, element] |
-| test.ps1:31:1:31:16 | [post] ...[...] [element] | semmle.label | [post] ...[...] [element] |
+| test.ps1:31:1:31:5 | [post] arr7 [unknown, unknown] | semmle.label | [post] arr7 [unknown, unknown] |
+| test.ps1:31:1:31:16 | [post] ...[...] [unknown] | semmle.label | [post] ...[...] [unknown] |
 | test.ps1:31:31:31:40 | Call to Source | semmle.label | Call to Source |
-| test.ps1:32:6:32:10 | arr7 [element, element] | semmle.label | arr7 [element, element] |
-| test.ps1:32:6:32:13 | ...[...] [element] | semmle.label | ...[...] [element] |
+| test.ps1:32:6:32:10 | arr7 [unknown, unknown] | semmle.label | arr7 [unknown, unknown] |
+| test.ps1:32:6:32:13 | ...[...] [unknown] | semmle.label | ...[...] [unknown] |
 | test.ps1:32:6:32:16 | ...[...] | semmle.label | ...[...] |
-| test.ps1:33:6:33:10 | arr7 [element, element] | semmle.label | arr7 [element, element] |
-| test.ps1:33:6:33:21 | ...[...] [element] | semmle.label | ...[...] [element] |
+| test.ps1:33:6:33:10 | arr7 [unknown, unknown] | semmle.label | arr7 [unknown, unknown] |
+| test.ps1:33:6:33:21 | ...[...] [unknown] | semmle.label | ...[...] [unknown] |
 | test.ps1:33:6:33:32 | ...[...] | semmle.label | ...[...] |
 | test.ps1:35:6:35:16 | Call to Source | semmle.label | Call to Source |
 | test.ps1:37:9:37:16 | ...,... [element 2] | semmle.label | ...,... [element 2] |
@@ -138,12 +138,12 @@ nodes
 | test.ps1:69:5:69:6 | x | semmle.label | x |
 | test.ps1:70:5:70:6 | y | semmle.label | y |
 | test.ps1:70:9:70:10 | z | semmle.label | z |
-| test.ps1:73:6:73:12 | Call to produce [element] | semmle.label | Call to produce [element] |
-| test.ps1:74:6:74:7 | x [element] | semmle.label | x [element] |
+| test.ps1:73:6:73:12 | Call to produce [unknown index] | semmle.label | Call to produce [unknown index] |
+| test.ps1:74:6:74:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:74:6:74:10 | ...[...] | semmle.label | ...[...] |
-| test.ps1:75:6:75:7 | x [element] | semmle.label | x [element] |
+| test.ps1:75:6:75:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:75:6:75:10 | ...[...] | semmle.label | ...[...] |
-| test.ps1:76:6:76:7 | x [element] | semmle.label | x [element] |
+| test.ps1:76:6:76:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:76:6:76:10 | ...[...] | semmle.label | ...[...] |
 | test.ps1:78:9:81:1 | ${...} [element a] | semmle.label | ${...} [element a] |
 | test.ps1:79:7:79:17 | Call to Source | semmle.label | Call to Source |
diff --git a/powershell/ql/test/library-tests/dataflow/local/flow.expected b/powershell/ql/test/library-tests/dataflow/local/flow.expected
index c436626f9186..b5b5ec1a1263 100644
--- a/powershell/ql/test/library-tests/dataflow/local/flow.expected
+++ b/powershell/ql/test/library-tests/dataflow/local/flow.expected
@@ -6,11 +6,11 @@
 | test.ps1:2:1:2:8 | Call to Sink | test.ps1:1:1:24:22 | pre-return value for {...} |
 | test.ps1:4:1:4:2 | b | test.ps1:5:4:5:5 | b |
 | test.ps1:4:6:4:12 | Call to GetBool | test.ps1:4:1:4:2 | b |
-| test.ps1:5:1:7:1 | phi | test.ps1:8:6:8:8 | a2 |
+| test.ps1:5:1:7:1 | phi (a2) | test.ps1:8:6:8:8 | a2 |
 | test.ps1:5:4:5:5 | b | test.ps1:10:14:10:15 | b |
-| test.ps1:6:5:6:7 | a2 | test.ps1:6:11:6:16 | [input] phi |
+| test.ps1:6:5:6:7 | a2 | test.ps1:6:11:6:16 | [input] phi (a2) |
 | test.ps1:6:11:6:16 | Call to Source | test.ps1:6:5:6:7 | a2 |
-| test.ps1:6:11:6:16 | [input] phi | test.ps1:5:1:7:1 | phi |
+| test.ps1:6:11:6:16 | [input] phi (a2) | test.ps1:5:1:7:1 | phi (a2) |
 | test.ps1:8:1:8:8 | Call to Sink | test.ps1:1:1:24:22 | pre-return value for {...} |
 | test.ps1:8:1:8:8 | Call to Sink | test.ps1:1:1:24:22 | pre-return value for {...} |
 | test.ps1:10:1:10:2 | c | test.ps1:11:6:11:7 | c |
diff --git a/powershell/ql/test/library-tests/dataflow/local/taint.expected b/powershell/ql/test/library-tests/dataflow/local/taint.expected
index 7e6eeb95740a..cc15a9b83d17 100644
--- a/powershell/ql/test/library-tests/dataflow/local/taint.expected
+++ b/powershell/ql/test/library-tests/dataflow/local/taint.expected
@@ -7,11 +7,11 @@
 | test.ps1:2:1:2:8 | Call to Sink | test.ps1:1:1:24:22 | pre-return value for {...} |
 | test.ps1:4:1:4:2 | b | test.ps1:5:4:5:5 | b |
 | test.ps1:4:6:4:12 | Call to GetBool | test.ps1:4:1:4:2 | b |
-| test.ps1:5:1:7:1 | phi | test.ps1:8:6:8:8 | a2 |
+| test.ps1:5:1:7:1 | phi (a2) | test.ps1:8:6:8:8 | a2 |
 | test.ps1:5:4:5:5 | b | test.ps1:10:14:10:15 | b |
-| test.ps1:6:5:6:7 | a2 | test.ps1:6:11:6:16 | [input] phi |
+| test.ps1:6:5:6:7 | a2 | test.ps1:6:11:6:16 | [input] phi (a2) |
 | test.ps1:6:11:6:16 | Call to Source | test.ps1:6:5:6:7 | a2 |
-| test.ps1:6:11:6:16 | [input] phi | test.ps1:5:1:7:1 | phi |
+| test.ps1:6:11:6:16 | [input] phi (a2) | test.ps1:5:1:7:1 | phi (a2) |
 | test.ps1:8:1:8:8 | Call to Sink | test.ps1:1:1:24:22 | pre-return value for {...} |
 | test.ps1:8:1:8:8 | Call to Sink | test.ps1:1:1:24:22 | pre-return value for {...} |
 | test.ps1:10:1:10:2 | c | test.ps1:11:6:11:7 | c |
diff --git a/powershell/ql/test/library-tests/dataflow/pipeline/test.expected b/powershell/ql/test/library-tests/dataflow/pipeline/test.expected
index 5e3b383e7cc9..b94675c879d6 100644
--- a/powershell/ql/test/library-tests/dataflow/pipeline/test.expected
+++ b/powershell/ql/test/library-tests/dataflow/pipeline/test.expected
@@ -3,24 +3,21 @@ edges
 | test.ps1:2:10:2:19 | Call to Source | test.ps1:5:5:5:6 | x | provenance |  |
 | test.ps1:3:10:3:19 | Call to Source | test.ps1:6:5:6:6 | y | provenance |  |
 | test.ps1:4:10:4:19 | Call to Source | test.ps1:6:9:6:10 | z | provenance |  |
-| test.ps1:5:5:5:6 | x | test.ps1:17:1:17:7 | Call to produce [element] | provenance |  |
-| test.ps1:6:5:6:6 | y | test.ps1:17:1:17:7 | Call to produce [element] | provenance |  |
-| test.ps1:6:9:6:10 | z | test.ps1:17:1:17:7 | Call to produce [element] | provenance |  |
+| test.ps1:5:5:5:6 | x | test.ps1:17:1:17:7 | Call to produce [unknown index] | provenance |  |
+| test.ps1:6:5:6:6 | y | test.ps1:17:1:17:7 | Call to produce [unknown index] | provenance |  |
+| test.ps1:6:9:6:10 | z | test.ps1:17:1:17:7 | Call to produce [unknown index] | provenance |  |
 | test.ps1:9:29:15:1 | [synth] pipeline [element 0] | test.ps1:12:5:14:5 | [synth] pipeline [element 0] | provenance |  |
 | test.ps1:9:29:15:1 | [synth] pipeline [element 1] | test.ps1:12:5:14:5 | [synth] pipeline [element 1] | provenance |  |
-| test.ps1:9:29:15:1 | [synth] pipeline [element] | test.ps1:12:5:14:5 | [synth] pipeline [element] | provenance |  |
+| test.ps1:9:29:15:1 | [synth] pipeline [unknown index] | test.ps1:12:5:14:5 | [synth] pipeline [unknown index] | provenance |  |
 | test.ps1:12:5:14:5 | [synth] pipeline [element 0] | test.ps1:13:9:13:15 | __pipeline_iterator | provenance |  |
 | test.ps1:12:5:14:5 | [synth] pipeline [element 1] | test.ps1:13:9:13:15 | __pipeline_iterator | provenance |  |
-| test.ps1:12:5:14:5 | [synth] pipeline [element] | test.ps1:13:9:13:15 | __pipeline_iterator | provenance |  |
-| test.ps1:17:1:17:7 | Call to produce [element] | test.ps1:9:29:15:1 | [synth] pipeline [element] | provenance |  |
-| test.ps1:17:1:17:7 | Call to produce [element] | test.ps1:17:1:17:7 | Call to produce [element] | provenance |  |
+| test.ps1:12:5:14:5 | [synth] pipeline [unknown index] | test.ps1:13:9:13:15 | __pipeline_iterator | provenance |  |
+| test.ps1:17:1:17:7 | Call to produce [unknown index] | test.ps1:9:29:15:1 | [synth] pipeline [unknown index] | provenance |  |
 | test.ps1:19:6:19:15 | Call to Source | test.ps1:21:1:21:2 | x | provenance |  |
 | test.ps1:20:6:20:15 | Call to Source | test.ps1:21:5:21:6 | y | provenance |  |
 | test.ps1:21:1:21:2 | x | test.ps1:21:1:21:6 | ...,... [element 0] | provenance |  |
 | test.ps1:21:1:21:6 | ...,... [element 0] | test.ps1:9:29:15:1 | [synth] pipeline [element 0] | provenance |  |
-| test.ps1:21:1:21:6 | ...,... [element 0] | test.ps1:21:1:21:6 | ...,... [element 0] | provenance |  |
 | test.ps1:21:1:21:6 | ...,... [element 1] | test.ps1:9:29:15:1 | [synth] pipeline [element 1] | provenance |  |
-| test.ps1:21:1:21:6 | ...,... [element 1] | test.ps1:21:1:21:6 | ...,... [element 1] | provenance |  |
 | test.ps1:21:5:21:6 | y | test.ps1:21:1:21:6 | ...,... [element 1] | provenance |  |
 | test.ps1:23:38:27:1 | [synth] pipeline [element 0] | test.ps1:24:5:26:5 | [synth] pipeline [element 0] | provenance |  |
 | test.ps1:23:38:27:1 | [synth] pipeline [element 1] | test.ps1:24:5:26:5 | [synth] pipeline [element 1] | provenance |  |
@@ -30,10 +27,26 @@ edges
 | test.ps1:30:6:30:15 | Call to Source | test.ps1:31:5:31:6 | y | provenance |  |
 | test.ps1:31:1:31:2 | x | test.ps1:31:1:31:6 | ...,... [element 0] | provenance |  |
 | test.ps1:31:1:31:6 | ...,... [element 0] | test.ps1:23:38:27:1 | [synth] pipeline [element 0] | provenance |  |
-| test.ps1:31:1:31:6 | ...,... [element 0] | test.ps1:31:1:31:6 | ...,... [element 0] | provenance |  |
 | test.ps1:31:1:31:6 | ...,... [element 1] | test.ps1:23:38:27:1 | [synth] pipeline [element 1] | provenance |  |
-| test.ps1:31:1:31:6 | ...,... [element 1] | test.ps1:31:1:31:6 | ...,... [element 1] | provenance |  |
 | test.ps1:31:5:31:6 | y | test.ps1:31:1:31:6 | ...,... [element 1] | provenance |  |
+| test.ps1:42:60:48:1 | x [element 0, element x] | test.ps1:45:5:47:5 | x [element 0, element x] | provenance |  |
+| test.ps1:42:60:48:1 | x [element 1, element x] | test.ps1:45:5:47:5 | x [element 1, element x] | provenance |  |
+| test.ps1:42:60:48:1 | x [element 2, element x] | test.ps1:45:5:47:5 | x [element 2, element x] | provenance |  |
+| test.ps1:45:5:47:5 | x [element 0, element x] | test.ps1:46:9:46:15 | __pipeline_iterator for x | provenance |  |
+| test.ps1:45:5:47:5 | x [element 1, element x] | test.ps1:46:9:46:15 | __pipeline_iterator for x | provenance |  |
+| test.ps1:45:5:47:5 | x [element 2, element x] | test.ps1:46:9:46:15 | __pipeline_iterator for x | provenance |  |
+| test.ps1:50:1:50:33 | [...]... [element x] | test.ps1:50:1:50:105 | ...,... [element 0, element x] | provenance |  |
+| test.ps1:50:1:50:105 | ...,... [element 0, element x] | test.ps1:42:60:48:1 | x [element 0, element x] | provenance |  |
+| test.ps1:50:1:50:105 | ...,... [element 1, element x] | test.ps1:42:60:48:1 | x [element 1, element x] | provenance |  |
+| test.ps1:50:1:50:105 | ...,... [element 2, element x] | test.ps1:42:60:48:1 | x [element 2, element x] | provenance |  |
+| test.ps1:50:17:50:33 | ${...} [element x] | test.ps1:50:1:50:33 | [...]... [element x] | provenance |  |
+| test.ps1:50:23:50:32 | Call to Source | test.ps1:50:17:50:33 | ${...} [element x] | provenance |  |
+| test.ps1:50:36:50:69 | [...]... [element x] | test.ps1:50:1:50:105 | ...,... [element 1, element x] | provenance |  |
+| test.ps1:50:52:50:69 | ${...} [element x] | test.ps1:50:36:50:69 | [...]... [element x] | provenance |  |
+| test.ps1:50:58:50:68 | Call to Source | test.ps1:50:52:50:69 | ${...} [element x] | provenance |  |
+| test.ps1:50:72:50:105 | [...]... [element x] | test.ps1:50:1:50:105 | ...,... [element 2, element x] | provenance |  |
+| test.ps1:50:88:50:105 | ${...} [element x] | test.ps1:50:72:50:105 | [...]... [element x] | provenance |  |
+| test.ps1:50:94:50:104 | Call to Source | test.ps1:50:88:50:105 | ${...} [element x] | provenance |  |
 nodes
 | test.ps1:2:10:2:19 | Call to Source | semmle.label | Call to Source |
 | test.ps1:3:10:3:19 | Call to Source | semmle.label | Call to Source |
@@ -43,19 +56,16 @@ nodes
 | test.ps1:6:9:6:10 | z | semmle.label | z |
 | test.ps1:9:29:15:1 | [synth] pipeline [element 0] | semmle.label | [synth] pipeline [element 0] |
 | test.ps1:9:29:15:1 | [synth] pipeline [element 1] | semmle.label | [synth] pipeline [element 1] |
-| test.ps1:9:29:15:1 | [synth] pipeline [element] | semmle.label | [synth] pipeline [element] |
+| test.ps1:9:29:15:1 | [synth] pipeline [unknown index] | semmle.label | [synth] pipeline [unknown index] |
 | test.ps1:12:5:14:5 | [synth] pipeline [element 0] | semmle.label | [synth] pipeline [element 0] |
 | test.ps1:12:5:14:5 | [synth] pipeline [element 1] | semmle.label | [synth] pipeline [element 1] |
-| test.ps1:12:5:14:5 | [synth] pipeline [element] | semmle.label | [synth] pipeline [element] |
+| test.ps1:12:5:14:5 | [synth] pipeline [unknown index] | semmle.label | [synth] pipeline [unknown index] |
 | test.ps1:13:9:13:15 | __pipeline_iterator | semmle.label | __pipeline_iterator |
-| test.ps1:17:1:17:7 | Call to produce [element] | semmle.label | Call to produce [element] |
-| test.ps1:17:1:17:7 | Call to produce [element] | semmle.label | Call to produce [element] |
+| test.ps1:17:1:17:7 | Call to produce [unknown index] | semmle.label | Call to produce [unknown index] |
 | test.ps1:19:6:19:15 | Call to Source | semmle.label | Call to Source |
 | test.ps1:20:6:20:15 | Call to Source | semmle.label | Call to Source |
 | test.ps1:21:1:21:2 | x | semmle.label | x |
 | test.ps1:21:1:21:6 | ...,... [element 0] | semmle.label | ...,... [element 0] |
-| test.ps1:21:1:21:6 | ...,... [element 0] | semmle.label | ...,... [element 0] |
-| test.ps1:21:1:21:6 | ...,... [element 1] | semmle.label | ...,... [element 1] |
 | test.ps1:21:1:21:6 | ...,... [element 1] | semmle.label | ...,... [element 1] |
 | test.ps1:21:5:21:6 | y | semmle.label | y |
 | test.ps1:23:38:27:1 | [synth] pipeline [element 0] | semmle.label | [synth] pipeline [element 0] |
@@ -67,16 +77,29 @@ nodes
 | test.ps1:30:6:30:15 | Call to Source | semmle.label | Call to Source |
 | test.ps1:31:1:31:2 | x | semmle.label | x |
 | test.ps1:31:1:31:6 | ...,... [element 0] | semmle.label | ...,... [element 0] |
-| test.ps1:31:1:31:6 | ...,... [element 0] | semmle.label | ...,... [element 0] |
-| test.ps1:31:1:31:6 | ...,... [element 1] | semmle.label | ...,... [element 1] |
 | test.ps1:31:1:31:6 | ...,... [element 1] | semmle.label | ...,... [element 1] |
 | test.ps1:31:5:31:6 | y | semmle.label | y |
+| test.ps1:42:60:48:1 | x [element 0, element x] | semmle.label | x [element 0, element x] |
+| test.ps1:42:60:48:1 | x [element 1, element x] | semmle.label | x [element 1, element x] |
+| test.ps1:42:60:48:1 | x [element 2, element x] | semmle.label | x [element 2, element x] |
+| test.ps1:45:5:47:5 | x [element 0, element x] | semmle.label | x [element 0, element x] |
+| test.ps1:45:5:47:5 | x [element 1, element x] | semmle.label | x [element 1, element x] |
+| test.ps1:45:5:47:5 | x [element 2, element x] | semmle.label | x [element 2, element x] |
+| test.ps1:46:9:46:15 | __pipeline_iterator for x | semmle.label | __pipeline_iterator for x |
+| test.ps1:50:1:50:33 | [...]... [element x] | semmle.label | [...]... [element x] |
+| test.ps1:50:1:50:105 | ...,... [element 0, element x] | semmle.label | ...,... [element 0, element x] |
+| test.ps1:50:1:50:105 | ...,... [element 1, element x] | semmle.label | ...,... [element 1, element x] |
+| test.ps1:50:1:50:105 | ...,... [element 2, element x] | semmle.label | ...,... [element 2, element x] |
+| test.ps1:50:17:50:33 | ${...} [element x] | semmle.label | ${...} [element x] |
+| test.ps1:50:23:50:32 | Call to Source | semmle.label | Call to Source |
+| test.ps1:50:36:50:69 | [...]... [element x] | semmle.label | [...]... [element x] |
+| test.ps1:50:52:50:69 | ${...} [element x] | semmle.label | ${...} [element x] |
+| test.ps1:50:58:50:68 | Call to Source | semmle.label | Call to Source |
+| test.ps1:50:72:50:105 | [...]... [element x] | semmle.label | [...]... [element x] |
+| test.ps1:50:88:50:105 | ${...} [element x] | semmle.label | ${...} [element x] |
+| test.ps1:50:94:50:104 | Call to Source | semmle.label | Call to Source |
 subpaths
 testFailures
-| test.ps1:36:13:36:30 | # $ hasValueFlow=8 | Missing result: hasValueFlow=8 |
-| test.ps1:46:17:46:66 | # $ hasValueFlow=9 hasValueFlow=10 hasValueFlow=11 | Missing result: hasValueFlow=9 |
-| test.ps1:46:17:46:66 | # $ hasValueFlow=9 hasValueFlow=10 hasValueFlow=11 | Missing result: hasValueFlow=10 |
-| test.ps1:46:17:46:66 | # $ hasValueFlow=9 hasValueFlow=10 hasValueFlow=11 | Missing result: hasValueFlow=11 |
 #select
 | test.ps1:13:9:13:15 | __pipeline_iterator | test.ps1:2:10:2:19 | Call to Source | test.ps1:13:9:13:15 | __pipeline_iterator | $@ | test.ps1:2:10:2:19 | Call to Source | Call to Source |
 | test.ps1:13:9:13:15 | __pipeline_iterator | test.ps1:3:10:3:19 | Call to Source | test.ps1:13:9:13:15 | __pipeline_iterator | $@ | test.ps1:3:10:3:19 | Call to Source | Call to Source |
@@ -85,3 +108,6 @@ testFailures
 | test.ps1:13:9:13:15 | __pipeline_iterator | test.ps1:20:6:20:15 | Call to Source | test.ps1:13:9:13:15 | __pipeline_iterator | $@ | test.ps1:20:6:20:15 | Call to Source | Call to Source |
 | test.ps1:25:9:25:15 | __pipeline_iterator | test.ps1:29:6:29:15 | Call to Source | test.ps1:25:9:25:15 | __pipeline_iterator | $@ | test.ps1:29:6:29:15 | Call to Source | Call to Source |
 | test.ps1:25:9:25:15 | __pipeline_iterator | test.ps1:30:6:30:15 | Call to Source | test.ps1:25:9:25:15 | __pipeline_iterator | $@ | test.ps1:30:6:30:15 | Call to Source | Call to Source |
+| test.ps1:46:9:46:15 | __pipeline_iterator for x | test.ps1:50:23:50:32 | Call to Source | test.ps1:46:9:46:15 | __pipeline_iterator for x | $@ | test.ps1:50:23:50:32 | Call to Source | Call to Source |
+| test.ps1:46:9:46:15 | __pipeline_iterator for x | test.ps1:50:58:50:68 | Call to Source | test.ps1:46:9:46:15 | __pipeline_iterator for x | $@ | test.ps1:50:58:50:68 | Call to Source | Call to Source |
+| test.ps1:46:9:46:15 | __pipeline_iterator for x | test.ps1:50:94:50:104 | Call to Source | test.ps1:46:9:46:15 | __pipeline_iterator for x | $@ | test.ps1:50:94:50:104 | Call to Source | Call to Source |
diff --git a/powershell/ql/test/library-tests/dataflow/pipeline/test.ps1 b/powershell/ql/test/library-tests/dataflow/pipeline/test.ps1
index d93bf1ba477e..8a55796e8726 100644
--- a/powershell/ql/test/library-tests/dataflow/pipeline/test.ps1
+++ b/powershell/ql/test/library-tests/dataflow/pipeline/test.ps1
@@ -33,7 +33,7 @@ $x, $y | consumeWithProcessAnonymous
 function consumeValueFromPipelineByPropertyNameWithoutProcess {
     Param([Parameter(ValueFromPipelineByPropertyName)] $x)
 
-    Sink $x # $ hasValueFlow=8
+    Sink $x # $ MISSING: hasValueFlow=8
 }
 
 $x = Source "8"
diff --git a/powershell/ql/test/library-tests/dataflow/returns/test.expected b/powershell/ql/test/library-tests/dataflow/returns/test.expected
index cfd34b3abcdd..6de78912cc4f 100644
--- a/powershell/ql/test/library-tests/dataflow/returns/test.expected
+++ b/powershell/ql/test/library-tests/dataflow/returns/test.expected
@@ -2,37 +2,37 @@ models
 edges
 | test.ps1:2:5:2:14 | Call to Source | test.ps1:5:6:5:19 | Call to callSourceOnce | provenance |  |
 | test.ps1:5:6:5:19 | Call to callSourceOnce | test.ps1:6:6:6:7 | x | provenance |  |
-| test.ps1:9:5:9:14 | Call to Source | test.ps1:13:6:13:20 | Call to callSourceTwice [element] | provenance |  |
-| test.ps1:10:5:10:14 | Call to Source | test.ps1:13:6:13:20 | Call to callSourceTwice [element] | provenance |  |
-| test.ps1:13:6:13:20 | Call to callSourceTwice [element] | test.ps1:15:6:15:7 | x [element] | provenance |  |
-| test.ps1:13:6:13:20 | Call to callSourceTwice [element] | test.ps1:16:6:16:7 | x [element] | provenance |  |
-| test.ps1:15:6:15:7 | x [element] | test.ps1:15:6:15:10 | ...[...] | provenance |  |
-| test.ps1:16:6:16:7 | x [element] | test.ps1:16:6:16:10 | ...[...] | provenance |  |
+| test.ps1:9:5:9:14 | Call to Source | test.ps1:13:6:13:20 | Call to callSourceTwice [unknown index] | provenance |  |
+| test.ps1:10:5:10:14 | Call to Source | test.ps1:13:6:13:20 | Call to callSourceTwice [unknown index] | provenance |  |
+| test.ps1:13:6:13:20 | Call to callSourceTwice [unknown index] | test.ps1:15:6:15:7 | x [unknown index] | provenance |  |
+| test.ps1:13:6:13:20 | Call to callSourceTwice [unknown index] | test.ps1:16:6:16:7 | x [unknown index] | provenance |  |
+| test.ps1:15:6:15:7 | x [unknown index] | test.ps1:15:6:15:10 | ...[...] | provenance |  |
+| test.ps1:16:6:16:7 | x [unknown index] | test.ps1:16:6:16:10 | ...[...] | provenance |  |
 | test.ps1:19:12:19:21 | Call to Source | test.ps1:22:6:22:18 | Call to returnSource1 | provenance |  |
 | test.ps1:22:6:22:18 | Call to returnSource1 | test.ps1:23:6:23:7 | x | provenance |  |
 | test.ps1:26:10:26:19 | Call to Source | test.ps1:27:5:27:6 | x | provenance |  |
-| test.ps1:27:5:27:6 | x | test.ps1:32:6:32:18 | Call to returnSource2 [element] | provenance |  |
+| test.ps1:27:5:27:6 | x | test.ps1:32:6:32:18 | Call to returnSource2 [unknown index] | provenance |  |
 | test.ps1:28:10:28:19 | Call to Source | test.ps1:29:12:29:13 | y | provenance |  |
-| test.ps1:29:12:29:13 | y | test.ps1:32:6:32:18 | Call to returnSource2 [element] | provenance |  |
-| test.ps1:32:6:32:18 | Call to returnSource2 [element] | test.ps1:33:6:33:7 | x [element] | provenance |  |
-| test.ps1:32:6:32:18 | Call to returnSource2 [element] | test.ps1:34:6:34:7 | x [element] | provenance |  |
-| test.ps1:33:6:33:7 | x [element] | test.ps1:33:6:33:10 | ...[...] | provenance |  |
-| test.ps1:34:6:34:7 | x [element] | test.ps1:34:6:34:10 | ...[...] | provenance |  |
-| test.ps1:38:9:38:18 | Call to Source | test.ps1:42:6:42:21 | Call to callSourceInLoop [element] | provenance |  |
-| test.ps1:42:6:42:21 | Call to callSourceInLoop [element] | test.ps1:43:6:43:7 | x [element] | provenance |  |
-| test.ps1:42:6:42:21 | Call to callSourceInLoop [element] | test.ps1:44:6:44:7 | x [element] | provenance |  |
-| test.ps1:43:6:43:7 | x [element] | test.ps1:43:6:43:10 | ...[...] | provenance |  |
-| test.ps1:44:6:44:7 | x [element] | test.ps1:44:6:44:10 | ...[...] | provenance |  |
+| test.ps1:29:12:29:13 | y | test.ps1:32:6:32:18 | Call to returnSource2 [unknown index] | provenance |  |
+| test.ps1:32:6:32:18 | Call to returnSource2 [unknown index] | test.ps1:33:6:33:7 | x [unknown index] | provenance |  |
+| test.ps1:32:6:32:18 | Call to returnSource2 [unknown index] | test.ps1:34:6:34:7 | x [unknown index] | provenance |  |
+| test.ps1:33:6:33:7 | x [unknown index] | test.ps1:33:6:33:10 | ...[...] | provenance |  |
+| test.ps1:34:6:34:7 | x [unknown index] | test.ps1:34:6:34:10 | ...[...] | provenance |  |
+| test.ps1:38:9:38:18 | Call to Source | test.ps1:42:6:42:21 | Call to callSourceInLoop [unknown index] | provenance |  |
+| test.ps1:42:6:42:21 | Call to callSourceInLoop [unknown index] | test.ps1:43:6:43:7 | x [unknown index] | provenance |  |
+| test.ps1:42:6:42:21 | Call to callSourceInLoop [unknown index] | test.ps1:44:6:44:7 | x [unknown index] | provenance |  |
+| test.ps1:43:6:43:7 | x [unknown index] | test.ps1:43:6:43:10 | ...[...] | provenance |  |
+| test.ps1:44:6:44:7 | x [unknown index] | test.ps1:44:6:44:10 | ...[...] | provenance |  |
 nodes
 | test.ps1:2:5:2:14 | Call to Source | semmle.label | Call to Source |
 | test.ps1:5:6:5:19 | Call to callSourceOnce | semmle.label | Call to callSourceOnce |
 | test.ps1:6:6:6:7 | x | semmle.label | x |
 | test.ps1:9:5:9:14 | Call to Source | semmle.label | Call to Source |
 | test.ps1:10:5:10:14 | Call to Source | semmle.label | Call to Source |
-| test.ps1:13:6:13:20 | Call to callSourceTwice [element] | semmle.label | Call to callSourceTwice [element] |
-| test.ps1:15:6:15:7 | x [element] | semmle.label | x [element] |
+| test.ps1:13:6:13:20 | Call to callSourceTwice [unknown index] | semmle.label | Call to callSourceTwice [unknown index] |
+| test.ps1:15:6:15:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:15:6:15:10 | ...[...] | semmle.label | ...[...] |
-| test.ps1:16:6:16:7 | x [element] | semmle.label | x [element] |
+| test.ps1:16:6:16:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:16:6:16:10 | ...[...] | semmle.label | ...[...] |
 | test.ps1:19:12:19:21 | Call to Source | semmle.label | Call to Source |
 | test.ps1:22:6:22:18 | Call to returnSource1 | semmle.label | Call to returnSource1 |
@@ -41,16 +41,16 @@ nodes
 | test.ps1:27:5:27:6 | x | semmle.label | x |
 | test.ps1:28:10:28:19 | Call to Source | semmle.label | Call to Source |
 | test.ps1:29:12:29:13 | y | semmle.label | y |
-| test.ps1:32:6:32:18 | Call to returnSource2 [element] | semmle.label | Call to returnSource2 [element] |
-| test.ps1:33:6:33:7 | x [element] | semmle.label | x [element] |
+| test.ps1:32:6:32:18 | Call to returnSource2 [unknown index] | semmle.label | Call to returnSource2 [unknown index] |
+| test.ps1:33:6:33:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:33:6:33:10 | ...[...] | semmle.label | ...[...] |
-| test.ps1:34:6:34:7 | x [element] | semmle.label | x [element] |
+| test.ps1:34:6:34:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:34:6:34:10 | ...[...] | semmle.label | ...[...] |
 | test.ps1:38:9:38:18 | Call to Source | semmle.label | Call to Source |
-| test.ps1:42:6:42:21 | Call to callSourceInLoop [element] | semmle.label | Call to callSourceInLoop [element] |
-| test.ps1:43:6:43:7 | x [element] | semmle.label | x [element] |
+| test.ps1:42:6:42:21 | Call to callSourceInLoop [unknown index] | semmle.label | Call to callSourceInLoop [unknown index] |
+| test.ps1:43:6:43:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:43:6:43:10 | ...[...] | semmle.label | ...[...] |
-| test.ps1:44:6:44:7 | x [element] | semmle.label | x [element] |
+| test.ps1:44:6:44:7 | x [unknown index] | semmle.label | x [unknown index] |
 | test.ps1:44:6:44:10 | ...[...] | semmle.label | ...[...] |
 subpaths
 testFailures