Thread safety analysis: Handle additional cast in scoped capability construction

We might have a CK_NoOp cast and a further CK_ConstructorConversion.
As an optimization, drop some IgnoreParens calls: inside of the
CK_{Constructor,UserDefined}Conversion should be no more parentheses,
and inside the CXXBindTemporaryExpr should also be none.

Lastly, we factor out the unpacking so that we can reuse it for
MaterializeTemporaryExprs later on.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D129752

Author: aaronpuchert

clang/lib/Analysis/ThreadSafety.cpp

@@ -2087,6 +2087,19 @@ static Expr *buildFakeCtorCall(CXXConstructorDecl *CD, ArrayRef<Expr *> Args,
                                   SourceRange(Loc, Loc));
 }
 
+static Expr *UnpackConstruction(Expr *E) {
+  if (auto *CE = dyn_cast<CastExpr>(E))
+    if (CE->getCastKind() == CK_NoOp)
+      E = CE->getSubExpr()->IgnoreParens();
+  if (auto *CE = dyn_cast<CastExpr>(E))
+    if (CE->getCastKind() == CK_ConstructorConversion ||
+        CE->getCastKind() == CK_UserDefinedConversion)
+      E = CE->getSubExpr();
+  if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))
+    E = BTE->getSubExpr();
+  return E;
+}
+
 void BuildLockset::VisitDeclStmt(const DeclStmt *S) {
   // adjust the context
   LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, S, LVarCtx);
@@ -2101,13 +2114,7 @@ void BuildLockset::VisitDeclStmt(const DeclStmt *S) {
       // handle constructors that involve temporaries
       if (auto *EWC = dyn_cast<ExprWithCleanups>(E))
         E = EWC->getSubExpr()->IgnoreParens();
-      if (auto *CE = dyn_cast<CastExpr>(E))
-        if (CE->getCastKind() == CK_NoOp ||
-            CE->getCastKind() == CK_ConstructorConversion ||
-            CE->getCastKind() == CK_UserDefinedConversion)
-          E = CE->getSubExpr()->IgnoreParens();
-      if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))
-        E = BTE->getSubExpr()->IgnoreParens();
+      E = UnpackConstruction(E);
 
       if (const auto *CE = dyn_cast<CXXConstructExpr>(E)) {
         const auto *CtorD = dyn_cast_or_null<NamedDecl>(CE->getConstructor());

clang/test/SemaCXX/warn-thread-safety-analysis.cpp

@@ -1683,6 +1683,13 @@ struct TestScopedLockable {
     a = 5;
   }
 
+#ifdef __cpp_guaranteed_copy_elision
+  void const_lock() {
+    const MutexLock mulock = MutexLock(&mu1);
+    a = 5;
+  }
+#endif
+
   void foo2() {
     ReaderMutexLock mulock1(&mu1);
     if (getBool()) {