unified: Make accessors introduce LocalVariables too

Author: asgerf

unified/ql/lib/codeql/unified/internal/LocalNameBinding.qll

@@ -409,6 +409,7 @@ module Public {
       |
         decl instanceof VariableDeclaration or
         decl instanceof FunctionDeclaration or // treat functions as values
+        decl instanceof AccessorDeclaration or
         decl instanceof Parameter or
         decl instanceof ForEachStmt or
         decl instanceof PatternGuardExpr or
@@ -446,6 +447,25 @@ module Public {
     }
   }
 
+  private AccessorDeclaration getAnAccessor(LocalVariable v) {
+    v.getABinding() = result.getNameNode() and
+    (result instanceof GetterDeclaration or result instanceof SetterDeclaration)
+  }
+
+  /** A local variable defined by a getter/setter pair, which does not store a value on its own. */
+  final class ComputedLocalVariable extends LocalVariable {
+    ComputedLocalVariable() { exists(getAnAccessor(this)) }
+
+    /** Gets the getter or setter for this computed variable. */
+    AccessorDeclaration getAnAccessor() { result = getAnAccessor(this) }
+
+    /** Gets the getter for this computed variable. */
+    GetterDeclaration getGetterDeclaration() { result = getAnAccessor(this) }
+
+    /** Gets the setter for this computed variable. */
+    SetterDeclaration getSetterDeclaration() { result = getAnAccessor(this) }
+  }
+
   /** An access to a locally-declared name. */
   class LocalNameAccess extends PotentialLocalNameAccess {
     LocalNameAccess() { not this instanceof UnqualifiedMemberAccess }

unified/ql/lib/codeql/unified/internal/dataflow/CaptureSsa.qll

@@ -21,7 +21,7 @@ module CaptureSsaInput implements InputSig<Location, BasicBlock> {
   Callable basicBlockGetEnclosingCallable(BasicBlock bb) { result = bb.getEnclosingCallable() }
 
   class CapturedVariable extends LocalVariable {
-    CapturedVariable() { this.isCaptured() }
+    CapturedVariable() { this.isCaptured() and not this instanceof ComputedLocalVariable }
 
     Callable getCallable() { result = super.getDeclaringCallable() }
   }

unified/ql/lib/codeql/unified/internal/dataflow/LocalSsa.qll

@@ -10,7 +10,7 @@ private import codeql.util.Void
 
 module LocalSsaInput implements InputSig<Location, BasicBlock> {
   class SourceVariable extends LocalVariable {
-    SourceVariable() { not this.isCaptured() }
+    SourceVariable() { not this.isCaptured() and not this instanceof ComputedLocalVariable }
   }
 
   predicate variableWrite(BasicBlock bb, int i, SourceVariable v, boolean certain) {