[Sema][ObjC] Don't warn about an implicitly retained self if the

retaining block and all of the enclosing blocks are non-escaping.

If the block implicitly retaining self doesn't escape, there is no risk
of creating retain cycles, so clang shouldn't diagnose it and force
users to add self-> to silence the diagnostic.

Also, fix a bug where clang was failing to diagnose an implicitly
retained self inside a c++ lambda nested inside a block.

rdar://problem/25059955

Differential Revision: https://reviews.llvm.org/D60736

llvm-svn: 358624

1 files changed, 31 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index fbe258bb1d5..8e0badf444a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13150,6 +13150,35 @@ private:
   bool IsLambda = false;
 };
 
+static void diagnoseImplicitlyRetainedSelf(Sema &S) {
+  llvm::DenseMap<const BlockDecl *, bool> EscapeInfo;
+
+  auto IsOrNestedInEscapingBlock = [&](const BlockDecl *BD) {
+    if (EscapeInfo.count(BD))
+      return EscapeInfo[BD];
+
+    bool R = false;
+    const BlockDecl *CurBD = BD;
+
+    do {
+      R = !CurBD->doesNotEscape();
+      if (R)
+        break;
+      CurBD = CurBD->getParent()->getInnermostBlockDecl();
+    } while (CurBD);
+
+    return EscapeInfo[BD] = R;
+  };
+
+  // If the location where 'self' is implicitly retained is inside a escaping
+  // block, emit a diagnostic.
+  for (const std::pair<SourceLocation, const BlockDecl *> &P :
+       S.ImplicitlyRetainedSelfLocs)
+    if (IsOrNestedInEscapingBlock(P.second))
+      S.Diag(P.first, diag::warn_implicitly_retains_self)
+          << FixItHint::CreateInsertion(P.first, "self->");
+}
+
 Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
                                     bool IsInstantiation) {
   FunctionDecl *FD = dcl ? dcl->getAsFunction() : nullptr;
@@ -13361,6 +13390,8 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
              diag::warn_objc_secondary_init_missing_init_call);
       getCurFunction()->ObjCWarnForNoInitDelegation = false;
     }
+
+    diagnoseImplicitlyRetainedSelf(*this);
   } else {
     // Parsing the function declaration failed in some way. Pop the fake scope
     // we pushed on.