Merge pull request #12907 from hvitved/ruby/destructured-assign-join

Ruby: Fix bad join in `DestructuredAssignDesugar`

Author: hvitved

ruby/ql/lib/codeql/ruby/ast/internal/Synthesis.qll

@@ -952,6 +952,8 @@ private module DestructuredAssignDesugar {
   }
 
   abstract private class LhsWithReceiver extends Expr {
+    LhsWithReceiver() { this = any(DestructuredAssignExpr dae).getElement(_) }
+
     abstract Expr getReceiver();
 
     abstract SynthKind getSynthKind();
@@ -960,8 +962,14 @@ private module DestructuredAssignDesugar {
   private class LhsCall extends LhsWithReceiver instanceof MethodCall {
     final override Expr getReceiver() { result = MethodCall.super.getReceiver() }
 
+    pragma[nomagic]
+    private string getMethodName(int args) {
+      result = super.getMethodName() and
+      args = super.getNumberOfArguments()
+    }
+
     final override SynthKind getSynthKind() {
-      result = MethodCallKind(super.getMethodName(), false, super.getNumberOfArguments())
+      exists(int args | result = MethodCallKind(this.getMethodName(args), false, args))
     }
   }
 
@@ -1154,9 +1162,7 @@ private module DestructuredAssignDesugar {
       )
     }
 
-    final override predicate excludeFromControlFlowTree(AstNode n) {
-      n = any(DestructuredAssignExpr tae).getElement(_).(LhsWithReceiver)
-    }
+    final override predicate excludeFromControlFlowTree(AstNode n) { n instanceof LhsWithReceiver }
   }
 }