From 92910f69a06e299beafb537ca08bc63e75a38612 Mon Sep 17 00:00:00 2001
From: Steven Wu <stevenwu@apple.com>
Date: Thu, 10 Mar 2016 02:02:48 +0000
Subject: [PATCH] Fix false positives for for-loop-analysis warning

Summary:
For PseudoObjectExpr, the DeclMatcher need to search only all the semantics
but also need to search pass OpaqueValueExpr for all potential uses for the
Decl.

Reviewers: thakis, rtrieu, rjmccall, doug.gregor

Subscribers: xazax.hun, rjmccall, doug.gregor, cfe-commits

Differential Revision: http://reviews.llvm.org/D17627

llvm-svn: 263087
---
 clang/lib/Sema/SemaStmt.cpp              | 12 ++++++++++++
 clang/test/SemaObjC/warn-loop-analysis.m | 15 +++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 clang/test/SemaObjC/warn-loop-analysis.m

diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index b73b4f088414..1975fcb11027 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -1440,6 +1440,18 @@ namespace {
           FoundDecl = true;
     }
 
+    void VisitPseudoObjectExpr(PseudoObjectExpr *POE) {
+      // Only need to visit the semantics for POE.
+      // SyntaticForm doesn't really use the Decal.
+      for (auto *S : POE->semantics()) {
+        if (auto *OVE = dyn_cast<OpaqueValueExpr>(S))
+          // Look past the OVE into the expression it binds.
+          Visit(OVE->getSourceExpr());
+        else
+          Visit(S);
+      }
+    }
+
     bool FoundDeclInUse() { return FoundDecl; }
 
   };  // end class DeclMatcher
diff --git a/clang/test/SemaObjC/warn-loop-analysis.m b/clang/test/SemaObjC/warn-loop-analysis.m
new file mode 100644
index 000000000000..8ae7375f7f2d
--- /dev/null
+++ b/clang/test/SemaObjC/warn-loop-analysis.m
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -Wloop-analysis -verify %s
+// expected-no-diagnostics
+
+@interface MyArray
+- (id)objectAtIndexedSubscript:(unsigned int)idx;
+@end
+
+// Do not warn on objc classes has objectAtIndexedSubscript method.
+MyArray *test;
+void foo()
+{
+  unsigned int i;
+  for (i = 42; i > 0;) // No warnings here
+    (void)test[--i];
+}