[PATCH] D87102: [Sema] Fix a -Warc-repeated-use-of-weak false-positive by only calling CheckPlaceholderExpr once

[Erik Pilkington via Phabricator via cfe-commits]

erik.pilkington created this revision.
erik.pilkington added reviewers: rjmccall, ahatanak, fhahn.
Herald added subscribers: ributzka, dexonsmith, jkorous.
erik.pilkington requested review of this revision.

Previously, this code discarded the result of CheckPlaceholderExpr for non-matrix subexpressions. Not only is this wasteful, but it was creating a Warc-repeated-use-of-weak false-positive on the attached testcase, since the discarded expression was still registered as a use of the weak property. (This was introduced in D76791 <https://reviews.llvm.org/D76791>)

rdar://66162246


https://reviews.llvm.org/D87102

Files:
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaObjC/arc-repeated-weak.mm


Index: clang/test/SemaObjC/arc-repeated-weak.mm
===================================================================
--- clang/test/SemaObjC/arc-repeated-weak.mm
+++ clang/test/SemaObjC/arc-repeated-weak.mm
@@ -485,3 +485,17 @@
 
 @class NSString;
 static NSString* const kGlobal = @"";
+
+ at interface NSDictionary
+- (id)objectForKeyedSubscript:(id)key;
+ at end
+
+ at interface WeakProp
+ at property (weak) NSDictionary *nd;
+ at end
+
+ at implementation WeakProp
+-(void)m {
+  (void)self.nd[@""]; // no warning
+}
+ at end
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -4607,34 +4607,13 @@
     return CreateBuiltinMatrixSubscriptExpr(
         matSubscriptE->getBase(), matSubscriptE->getRowIdx(), idx, rbLoc);
   }
-  Expr *matrixBase = base;
-  bool IsMSPropertySubscript = isMSPropertySubscriptExpr(*this, base);
-  if (!IsMSPropertySubscript) {
-    ExprResult result = CheckPlaceholderExpr(base);
-    if (!result.isInvalid())
-      matrixBase = result.get();
-  }
-  if (matrixBase->getType()->isMatrixType()) {
-    if (CheckAndReportCommaError(idx))
-      return ExprError();
-
-    return CreateBuiltinMatrixSubscriptExpr(matrixBase, idx, nullptr, rbLoc);
-  }
-
-  // A comma-expression as the index is deprecated in C++2a onwards.
-  if (getLangOpts().CPlusPlus20 &&
-      ((isa<BinaryOperator>(idx) && cast<BinaryOperator>(idx)->isCommaOp()) ||
-       (isa<CXXOperatorCallExpr>(idx) &&
-        cast<CXXOperatorCallExpr>(idx)->getOperator() == OO_Comma))) {
-    Diag(idx->getExprLoc(), diag::warn_deprecated_comma_subscript)
-      << SourceRange(base->getBeginLoc(), rbLoc);
-  }
 
   // Handle any non-overload placeholder types in the base and index
   // expressions.  We can't handle overloads here because the other
   // operand might be an overloadable type, in which case the overload
   // resolution for the operator overload should get the first crack
   // at the overload.
+  bool IsMSPropertySubscript = false;
   if (base->getType()->isNonOverloadPlaceholderType()) {
     IsMSPropertySubscript = isMSPropertySubscriptExpr(*this, base);
     if (!IsMSPropertySubscript) {
@@ -4644,6 +4623,23 @@
       base = result.get();
     }
   }
+
+  if (base->getType()->isMatrixType()) {
+    if (CheckAndReportCommaError(idx))
+      return ExprError();
+
+    return CreateBuiltinMatrixSubscriptExpr(base, idx, nullptr, rbLoc);
+  }
+
+  // A comma-expression as the index is deprecated in C++2a onwards.
+  if (getLangOpts().CPlusPlus20 &&
+      ((isa<BinaryOperator>(idx) && cast<BinaryOperator>(idx)->isCommaOp()) ||
+       (isa<CXXOperatorCallExpr>(idx) &&
+        cast<CXXOperatorCallExpr>(idx)->getOperator() == OO_Comma))) {
+    Diag(idx->getExprLoc(), diag::warn_deprecated_comma_subscript)
+        << SourceRange(base->getBeginLoc(), rbLoc);
+  }
+
   if (idx->getType()->isNonOverloadPlaceholderType()) {
     ExprResult result = CheckPlaceholderExpr(idx);
     if (result.isInvalid()) return ExprError();


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D87102.289764.patch
Type: text/x-patch
Size: 3059 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20200903/38b18828/attachment.bin>