[PATCH] D55662: [Sema][ObjC] Do not warn about repeated uses of weak variables when the variables are accessed in an unevaluated context.

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak created this revision.
ahatanak added reviewers: erik.pilkington, rjmccall, rsmith.
ahatanak added a project: clang.
Herald added subscribers: dexonsmith, jkorous.

Sema shouldn't record uses of weak variables when they are used in an unevaluated context.

For example:

  decltype([obj weakProp]) 
  decltype(objc.weakProp)
  __typeof__(objc.weakProp)

rdar://problem/45742525


Repository:
  rC Clang

https://reviews.llvm.org/D55662

Files:
  lib/Sema/SemaExprObjC.cpp
  lib/Sema/SemaType.cpp
  test/SemaObjC/arc-repeated-weak.mm


Index: test/SemaObjC/arc-repeated-weak.mm
===================================================================
--- test/SemaObjC/arc-repeated-weak.mm
+++ test/SemaObjC/arc-repeated-weak.mm
@@ -462,6 +462,9 @@
   NSString * t2 = NSBundle.foo2.prop;
   use(NSBundle.foo2.weakProp); // expected-warning{{weak property 'weakProp' may be accessed multiple times}}
   use(NSBundle2.foo2.weakProp); // expected-note{{also accessed here}}
+  decltype([NSBundle2.foo2 weakProp]) t3;
+  decltype(NSBundle2.foo2.weakProp) t4;
+  __typeof__(NSBundle2.foo2.weakProp) t5;
 }
 
 // This used to crash in the constructor of WeakObjectProfileTy when a
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -8040,6 +8040,8 @@
 }
 
 QualType Sema::BuildTypeofExprType(Expr *E, SourceLocation Loc) {
+  EnterExpressionEvaluationContext Unevaluated(
+      *this, ExpressionEvaluationContext::Unevaluated);
   ExprResult ER = CheckPlaceholderExpr(E);
   if (ER.isInvalid()) return QualType();
   E = ER.get();
@@ -8127,6 +8129,9 @@
 
 QualType Sema::BuildDecltypeType(Expr *E, SourceLocation Loc,
                                  bool AsUnevaluated) {
+  EnterExpressionEvaluationContext Unevaluated(
+      *this, ExpressionEvaluationContext::Unevaluated);
+
   ExprResult ER = CheckPlaceholderExpr(E);
   if (ER.isInvalid()) return QualType();
   E = ER.get();
Index: lib/Sema/SemaExprObjC.cpp
===================================================================
--- lib/Sema/SemaExprObjC.cpp
+++ lib/Sema/SemaExprObjC.cpp
@@ -3140,7 +3140,7 @@
           Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_weak;
         if (!IsWeak && Sel.isUnarySelector())
           IsWeak = ReturnType.getObjCLifetime() & Qualifiers::OCL_Weak;
-        if (IsWeak &&
+        if (IsWeak && !isUnevaluatedContext() &&
             !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, LBracLoc))
           getCurFunction()->recordUseOfWeak(Result, Prop);
       }


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