Sync to upstream/release/606

Analysis/include/Luau/ConstraintGenerator.h

@@ -150,7 +150,7 @@ struct ConstraintGenerator
      */
     ScopePtr childScope(AstNode* node, const ScopePtr& parent);
 
-    std::optional<TypeId> lookup(Scope* scope, DefId def);
+    std::optional<TypeId> lookup(Scope* scope, DefId def, bool prototype = true);
 
     /**
      * Adds a new constraint with no dependencies to a given scope.

Analysis/include/Luau/DataFlowGraph.h

@@ -74,8 +74,15 @@ struct DataFlowGraph
 
 struct DfgScope
 {
+    enum ScopeType
+    {
+        Linear,
+        Loop,
+        Function,
+    };
+
     DfgScope* parent;
-    bool isLoopScope;
+    ScopeType scopeType;
 
     using Bindings = DenseHashMap<Symbol, const Def*>;
     using Props = DenseHashMap<const Def*, std::unordered_map<std::string, const Def*>>;
@@ -117,7 +124,17 @@ struct DataFlowGraphBuilder
 
     std::vector<std::unique_ptr<DfgScope>> scopes;
 
-    DfgScope* childScope(DfgScope* scope, bool isLoopScope = false);
+    struct FunctionCapture
+    {
+        std::vector<DefId> captureDefs;
+        std::vector<DefId> allVersions;
+        size_t versionOffset = 0;
+    };
+
+    DenseHashMap<Symbol, FunctionCapture> captures{Symbol{}};
+    void resolveCaptures();
+
+    DfgScope* childScope(DfgScope* scope, DfgScope::ScopeType scopeType = DfgScope::Linear);
 
     void join(DfgScope* p, DfgScope* a, DfgScope* b);
     void joinBindings(DfgScope::Bindings& p, const DfgScope::Bindings& a, const DfgScope::Bindings& b);
@@ -167,11 +184,11 @@ struct DataFlowGraphBuilder
     DataFlowResult visitExpr(DfgScope* scope, AstExprError* error);
 
     void visitLValue(DfgScope* scope, AstExpr* e, DefId incomingDef, bool isCompoundAssignment = false);
-    void visitLValue(DfgScope* scope, AstExprLocal* l, DefId incomingDef, bool isCompoundAssignment);
-    void visitLValue(DfgScope* scope, AstExprGlobal* g, DefId incomingDef, bool isCompoundAssignment);
-    void visitLValue(DfgScope* scope, AstExprIndexName* i, DefId incomingDef);
-    void visitLValue(DfgScope* scope, AstExprIndexExpr* i, DefId incomingDef);
-    void visitLValue(DfgScope* scope, AstExprError* e, DefId incomingDef);
+    DefId visitLValue(DfgScope* scope, AstExprLocal* l, DefId incomingDef, bool isCompoundAssignment);
+    DefId visitLValue(DfgScope* scope, AstExprGlobal* g, DefId incomingDef, bool isCompoundAssignment);
+    DefId visitLValue(DfgScope* scope, AstExprIndexName* i, DefId incomingDef);
+    DefId visitLValue(DfgScope* scope, AstExprIndexExpr* i, DefId incomingDef);
+    DefId visitLValue(DfgScope* scope, AstExprError* e, DefId incomingDef);
 
     void visitType(DfgScope* scope, AstType* t);
     void visitType(DfgScope* scope, AstTypeReference* r);

Analysis/include/Luau/Def.h

@@ -73,6 +73,7 @@ const T* get(DefId def)
 }
 
 bool containsSubscriptedDefinition(DefId def);
+void collectOperands(DefId def, std::vector<DefId>* operands);
 
 struct DefArena
 {

Analysis/src/ConstraintGenerator.cpp

@@ -205,30 +205,32 @@ ScopePtr ConstraintGenerator::childScope(AstNode* node, const ScopePtr& parent)
     return scope;
 }
 
-std::optional<TypeId> ConstraintGenerator::lookup(Scope* scope, DefId def)
+std::optional<TypeId> ConstraintGenerator::lookup(Scope* scope, DefId def, bool prototype)
 {
     if (get<Cell>(def))
         return scope->lookup(def);
     if (auto phi = get<Phi>(def))
     {
         if (auto found = scope->lookup(def))
             return *found;
+        else if (!prototype)
+            return std::nullopt;
 
         TypeId res = builtinTypes->neverType;
 
         for (DefId operand : phi->operands)
         {
-            // `scope->lookup(operand)` may return nothing because it could be a phi node of globals, but one of
-            // the operand of that global has never been assigned a type, and so it should be an error.
-            // e.g.
-            // ```
-            // if foo() then
-            //   g = 5
-            // end
-            // -- `g` here is a phi node of the assignment to `g`, or the original revision of `g` before the branch.
-            // ```
-            TypeId ty = scope->lookup(operand).value_or(builtinTypes->errorRecoveryType());
-            res = simplifyUnion(builtinTypes, arena, res, ty).result;
+            // `scope->lookup(operand)` may return nothing because we only bind a type to that operand
+            // once we've seen that particular `DefId`. In this case, we need to prototype those types
+            // and use those at a later time.
+            std::optional<TypeId> ty = lookup(scope, operand, /*prototype*/false);
+            if (!ty)
+            {
+                ty = arena->addType(BlockedType{});
+                rootScope->lvalueTypes[operand] = *ty;
+            }
+
+            res = simplifyUnion(builtinTypes, arena, res, *ty).result;
         }
 
         scope->lvalueTypes[def] = res;
@@ -861,7 +863,7 @@ ControlFlow ConstraintGenerator::visit(const ScopePtr& scope, AstStatFunction* f
     DenseHashSet<Constraint*> excludeList{nullptr};
 
     DefId def = dfg->getDef(function->name);
-    std::optional<TypeId> existingFunctionTy = scope->lookup(def);
+    std::optional<TypeId> existingFunctionTy = lookup(scope.get(), def);
 
     if (AstExprLocal* localName = function->name->as<AstExprLocal>())
     {
@@ -1724,16 +1726,14 @@ Inference ConstraintGenerator::check(const ScopePtr& scope, AstExprGlobal* globa
     /* prepopulateGlobalScope() has already added all global functions to the environment by this point, so any
      * global that is not already in-scope is definitely an unknown symbol.
      */
-    if (auto ty = lookup(scope.get(), def))
-        return Inference{*ty, refinementArena.proposition(key, builtinTypes->truthyType)};
-    else if (auto ty = scope->lookup(global->name))
+    if (auto ty = lookup(scope.get(), def, /*prototype=*/false))
     {
         rootScope->lvalueTypes[def] = *ty;
         return Inference{*ty, refinementArena.proposition(key, builtinTypes->truthyType)};
     }
     else
     {
-        reportError(global->location, UnknownSymbol{global->name.value});
+        reportError(global->location, UnknownSymbol{global->name.value, UnknownSymbol::Binding});
         return Inference{builtinTypes->errorRecoveryType()};
     }
 }
@@ -3110,6 +3110,16 @@ struct GlobalPrepopulator : AstVisitor
 
         return true;
     }
+
+    bool visit(AstType*) override
+    {
+        return true;
+    }
+
+    bool visit(class AstTypePack* node) override
+    {
+        return true;
+    }
 };
 
 void ConstraintGenerator::prepopulateGlobalScope(const ScopePtr& globalScope, AstStatBlock* program)