Rust: Fix variable access overlap

rust/ql/consistency-queries/VariableConsistency.ql

@@ -0,0 +1,8 @@
+/**
+ * @name Variable inconsistencies
+ * @description Lists the variable inconsistencies in the database.  This query is intended for internal use.
+ * @kind table
+ * @id rust/diagnostics/variable-consistency
+ */
+
+import codeql.rust.internal.VariableConsistency

rust/ql/lib/codeql/rust/elements/internal/VariableImpl.qll

@@ -460,7 +460,12 @@ module Impl {
     VariableAccessCand cand, VariableScope scope, string name, int nestLevel, int ord
   ) {
     name = cand.getName() and
-    scope = [cand.(VariableScope), getEnclosingScope(cand)] and
+    (
+      scope = cand
+      or
+      not cand instanceof VariableScope and
+      scope = getEnclosingScope(cand)
+    ) and
     ord = getPreOrderNumbering(scope, cand) and
     nestLevel = 0
     or

rust/ql/lib/codeql/rust/internal/VariableConsistency.qll

@@ -0,0 +1,10 @@
+/**
+ * Provides logic for recognizing variable inconsistencies.
+ */
+
+private import rust
+
+query predicate multipleVariableTargets(VariableAccess va, Variable v1) {
+  va = v1.getAnAccess() and
+  strictcount(va.getVariable()) > 1
+}

rust/ql/test/library-tests/variables/main.rs

@@ -360,6 +360,15 @@ fn match_pattern14() {
     }
 }
 
+fn match_pattern15() {
+    let x = Some(0); // x1
+    match x { // $ read_access=x1
+            Some(x) // x2
+                => x, // $ read_access=x2
+            _ => 0
+        };
+}
+
 fn param_pattern1(
     a8: &str, // a8
     (
@@ -757,6 +766,7 @@ fn main() {
     match_pattern12();
     match_pattern13();
     match_pattern14();
+    match_pattern15();
     param_pattern1("a", ("b", "c"));
     param_pattern2(Either::Left(45));
     destruct_assignment();