IdentifierHidden: add heuristic for hiding in lambda

Author: knewbury01

cpp/common/src/codingstandards/cpp/rules/identifierhidden/IdentifierHidden.qll

@@ -11,6 +11,25 @@ abstract class IdentifierHiddenSharedQuery extends Query { }
 
 Query getQuery() { result instanceof IdentifierHiddenSharedQuery }
 
+/**
+ * There is a lambda that contains a declaration
+ * that hides something that is captured
+ * and the lambda exists in the function where this lamda is enclosed
+ */
+predicate hiddenInLambda(UserDeclaration v2, UserDeclaration v1) {
+  exists(Scope s, Closure le |
+    s.getADeclaration() = v2 and
+    s.getAnAncestor() = le and
+    le.getEnclosingFunction().getBasicBlock().(Scope) = v1.getParentScope() and
+    exists(LambdaCapture cap, Variable v |
+      v.getAnAccess() = cap.getInitializer().(VariableAccess) and
+      v = v1 and
+      le.getLambdaExpression().getACapture() = cap
+    ) and
+    v2.getName() = v1.getName()
+  )
+}
+
 query predicate problems(UserDeclaration v2, string message, UserDeclaration v1, string varName) {
   not isExcluded(v1, getQuery()) and
   not isExcluded(v2, getQuery()) and
@@ -20,7 +39,7 @@ query predicate problems(UserDeclaration v2, string message, UserDeclaration v1,
   //ignore types for this rule
   not v2 instanceof Type and
   not v1 instanceof Type and
-  hidesStrict(v1, v2) and
+  (hidesStrict(v1, v2) or hiddenInLambda(v2, v1)) and
   not excludedViaNestedNamespaces(v2, v1) and
   varName = v1.getName() and
   message = "Declaration is hiding declaration $@."

cpp/common/test/rules/identifierhidden/IdentifierHidden.expected

@@ -9,3 +9,4 @@
 | test.cpp:70:12:70:12 | i | Declaration is hiding declaration $@. | test.cpp:61:7:61:7 | i | i |
 | test.cpp:75:16:75:16 | i | Declaration is hiding declaration $@. | test.cpp:61:7:61:7 | i | i |
 | test.cpp:81:5:81:5 | a | Declaration is hiding declaration $@. | test.cpp:79:5:79:5 | a | a |
+| test.cpp:102:9:102:9 | b | Declaration is hiding declaration $@. | test.cpp:96:11:96:11 | b | b |

cpp/common/test/rules/identifierhidden/test.cpp

@@ -99,7 +99,7 @@ void f4() {
   };
 
   auto lambda2 = [b]() {
-    int b = 10; // NON_COMPLIANT[FALSE_NEGATIVE] - not an exception - captured
+    int b = 10; // NON_COMPLIANT - not an exception - captured
                 // variable b
   };
 }