From 433c2e64f851849737f108371ebddc97e582ee8e Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Thu, 21 Mar 2013 00:10:07 +0000
Subject: [PATCH] Further weaken block conversion rules to permit blocks with
 enum return type to be converted to blocks with any integer type of the same
 size.

rdar://13463504

llvm-svn: 177613
---
 clang/lib/AST/ASTContext.cpp   | 35 +++++++++++++++++++++++++----------
 clang/test/Sema/block-return.c | 11 +++++++++++
 clang/test/SemaObjC/blocks.m   |  4 ++--
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index b55a926..eee7ed2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -6844,6 +6844,27 @@ QualType ASTContext::mergeFunctionTypes(QualType lhs, QualType rhs,
   return getFunctionNoProtoType(retType, einfo);
 }
 
+/// Given that we have an enum type and a non-enum type, try to merge them.
+static QualType mergeEnumWithInteger(ASTContext &Context, const EnumType *ET,
+                                     QualType other, bool isBlockReturnType) {
+  // C99 6.7.2.2p4: Each enumerated type shall be compatible with char,
+  // a signed integer type, or an unsigned integer type.
+  // Compatibility is based on the underlying type, not the promotion
+  // type.
+  QualType underlyingType = ET->getDecl()->getIntegerType();
+  if (underlyingType.isNull()) return QualType();
+  if (Context.hasSameType(underlyingType, other))
+    return other;
+
+  // In block return types, we're more permissive and accept any
+  // integral type of the same size.
+  if (isBlockReturnType && other->isIntegerType() &&
+      Context.getTypeSize(underlyingType) == Context.getTypeSize(other))
+    return other;
+
+  return QualType();
+}
+
 QualType ASTContext::mergeTypes(QualType LHS, QualType RHS, 
                                 bool OfBlockPointer,
                                 bool Unqualified, bool BlockReturnType) {
@@ -6925,19 +6946,13 @@ QualType ASTContext::mergeTypes(QualType LHS, QualType RHS,
 
   // If the canonical type classes don't match.
   if (LHSClass != RHSClass) {
-    // C99 6.7.2.2p4: Each enumerated type shall be compatible with char,
-    // a signed integer type, or an unsigned integer type.
-    // Compatibility is based on the underlying type, not the promotion
-    // type.
+    // Note that we only have special rules for turning block enum
+    // returns into block int returns, not vice-versa.
     if (const EnumType* ETy = LHS->getAs<EnumType>()) {
-      QualType TINT = ETy->getDecl()->getIntegerType();
-      if (!TINT.isNull() && hasSameType(TINT, RHSCan.getUnqualifiedType()))
-        return RHS;
+      return mergeEnumWithInteger(*this, ETy, RHS, false);
     }
     if (const EnumType* ETy = RHS->getAs<EnumType>()) {
-      QualType TINT = ETy->getDecl()->getIntegerType();
-      if (!TINT.isNull() && hasSameType(TINT, LHSCan.getUnqualifiedType()))
-        return LHS;
+      return mergeEnumWithInteger(*this, ETy, LHS, BlockReturnType);
     }
     // allow block pointer type to match an 'id' type.
     if (OfBlockPointer && !BlockReturnType) {
diff --git a/clang/test/Sema/block-return.c b/clang/test/Sema/block-return.c
index 2ea4d81..6b4d998 100644
--- a/clang/test/Sema/block-return.c
+++ b/clang/test/Sema/block-return.c
@@ -134,3 +134,14 @@ void foo7()
 void (^blk)(void) = ^{
     return (void)0; // expected-warning {{void block literal should not return void expression}}
 };
+
+// rdar://13463504
+enum Test8 { T8_a, T8_b, T8_c };
+void test8(void) {
+  extern void test8_helper(int (^)(int));
+  test8_helper(^(int flag) { if (flag) return T8_a; return T8_b; });
+}
+void test8b(void) {
+  extern void test8_helper2(char (^)(int)); // expected-note {{here}}
+  test8_helper2(^(int flag) { if (flag) return T8_a; return T8_b; }); // expected-error {{passing 'enum Test8 (^)(int)' to parameter of type 'char (^)(int)'}}
+}
diff --git a/clang/test/SemaObjC/blocks.m b/clang/test/SemaObjC/blocks.m
index dd659ad..b523e4c 100644
--- a/clang/test/SemaObjC/blocks.m
+++ b/clang/test/SemaObjC/blocks.m
@@ -196,8 +196,8 @@ typedef short (^short_block_t)();
 void testAnonymousEnumTypes(int arg) {
   int_block_t IB;
   IB = ^{ return AnonymousValue; };
-  IB = ^{ if (arg) return TDE_Value; else return getTDE(); }; // expected-error {{incompatible block pointer}}
-  IB = ^{ if (arg) return getTDE(); else return TDE_Value; }; // expected-error {{incompatible block pointer}}
+  IB = ^{ if (arg) return TDE_Value; else return getTDE(); };
+  IB = ^{ if (arg) return getTDE(); else return TDE_Value; };
 
   // Since we fixed the underlying type of the enum, these are considered
   // compatible block types anyway.
-- 
2.7.4