IdentifierHidden: remove lambda special casing

This removes the special handling of lambda expressions, which
was causing performance issues.

Instead, we rely on the new behviour of the Scope library, which
calculates identifier hiding for lambda expressions as part of the
main calculation.

This has one semantic change - the new code applies
`isInSameTranslationUnit`, which reduces false positives where the
identifier "hiding" in a lambda occurred with an outer variable in
a different translation unit.

Author: lcartey

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

@@ -9,75 +9,11 @@ import cpp
 import codingstandards.cpp.Customizations
 import codingstandards.cpp.Exclusions
 import codingstandards.cpp.Scope
-import codingstandards.cpp.ConstHelpers
 
 abstract class IdentifierHiddenSharedQuery extends Query { }
 
 Query getQuery() { result instanceof IdentifierHiddenSharedQuery }
 
-/**
- * a `Variable` that is nonvolatile and const
- * and of type `IntegralOrEnumType`
- */
-class NonVolatileConstIntegralOrEnumVariable extends Variable {
-  NonVolatileConstIntegralOrEnumVariable() {
-    not this.isVolatile() and
-    this.isConst() and
-    this.getUnspecifiedType() instanceof IntegralOrEnumType
-  }
-}
-
-/**
- * Holds if declaration `innerDecl`, declared in a lambda, hides a declaration `outerDecl` by the lambda.
- */
-predicate hiddenInLambda(UserVariable outerDecl, UserVariable innerDecl) {
-  exists(
-    Scope innerScope, LambdaExpression lambdaExpr, Scope lambdaExprScope, Scope outerScope,
-    Closure lambdaClosure
-  |
-    // The variable `innerDecl` is declared inside of the lambda.
-    innerScope.getADeclaration() = innerDecl and
-    // Because a lambda is compiled down to a closure, we need to use the closure to determine if the declaration
-    // is part of the lambda.
-    innerScope.getAnAncestor() = lambdaClosure and
-    // Next we determine the scope of the lambda expression to determine if `outerDecl` is visible in the scope of the lambda.
-    lambdaClosure.getLambdaExpression() = lambdaExpr and
-    lambdaExprScope.getAnExpr() = lambdaExpr and
-    outerScope.getADeclaration() = outerDecl and
-    lambdaExprScope.getStrictParent*() = outerScope and
-    (
-      // A definition can be hidden if it is in scope and it is captured by the lambda,
-      exists(LambdaCapture cap |
-        lambdaExpr.getACapture() = cap and
-        // The outer declaration is captured by the lambda
-        outerDecl.getAnAccess() = cap.getInitializer()
-      )
-      or
-      // it is is non-local,
-      outerDecl instanceof GlobalVariable
-      or
-      // it has static or thread local storage duration,
-      (outerDecl.isThreadLocal() or outerDecl.isStatic())
-      or
-      //it is a reference that has been initialized with a constant expression.
-      outerDecl.getType().stripTopLevelSpecifiers() instanceof ReferenceType and
-      outerDecl.getInitializer().getExpr() instanceof Literal
-      or
-      // //it const non-volatile integral or enumeration type and has been initialized with a constant expression
-      outerDecl instanceof NonVolatileConstIntegralOrEnumVariable and
-      outerDecl.getInitializer().getExpr() instanceof Literal
-      or
-      //it is constexpr and has no mutable members
-      outerDecl.isConstexpr() and
-      not exists(Class c |
-        c = outerDecl.getType() and not c.getAMember() instanceof MutableVariable
-      )
-    ) and
-    // Finally, the variables must have the same names.
-    innerDecl.getName() = outerDecl.getName()
-  )
-}
-
 query predicate problems(
   UserVariable innerDecl, string message, UserVariable outerDecl, string varName
 ) {
@@ -86,7 +22,7 @@ query predicate problems(
   //ignore template variables for this rule
   not outerDecl instanceof TemplateVariable and
   not innerDecl instanceof TemplateVariable and
-  (hidesStrict(outerDecl, innerDecl) or hiddenInLambda(outerDecl, innerDecl)) and
+  hidesStrict(outerDecl, innerDecl) and
   not excludedViaNestedNamespaces(outerDecl, innerDecl) and
   varName = outerDecl.getName() and
   message = "Variable is hiding variable $@."