Merging r228792:

------------------------------------------------------------------------
r228792 | rsmith | 2015-02-10 18:41:33 -0800 (Tue, 10 Feb 2015) | 5 lines

Add a warning for direct-list-initialization of a variable with a deduced type
(or of a lambda init-capture, which is sort-of such a variable). The semantics
of such constructs will change when we implement N3922, so we intend to warn on
this in Clang 3.6 then change the semantics in Clang 3.7.

------------------------------------------------------------------------


git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_36@228799 91177308-0d34-0410-b5e6-96231b3b80d8

9 files changed, 32 insertions, 7 deletions

diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 5edd3ddbc8..2681ada248 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -749,3 +749,6 @@ def SerializedDiagnostics : DiagGroup<"serialized-diagnostics">;
 // A warning group for warnings about code that clang accepts when
 // compiling CUDA C/C++ but which is not compatible with the CUDA spec.
 def CudaCompat : DiagGroup<"cuda-compat">;
+
+// A warning group for things that will change semantics in the future.
+def FutureCompat : DiagGroup<"future-compat">;
diff --git a/include/clang/Basic/DiagnosticParseKinds.td b/include/clang/Basic/DiagnosticParseKinds.td
index 239d4d20bb..eca5f13811 100644
--- a/include/clang/Basic/DiagnosticParseKinds.td
+++ b/include/clang/Basic/DiagnosticParseKinds.td
@@ -802,6 +802,10 @@ def warn_cxx98_compat_lambda : Warning<
 def err_lambda_missing_parens : Error<
   "lambda requires '()' before %select{'mutable'|return type|"
   "attribute specifier}0">;
+def warn_init_capture_direct_list_init : Warning<
+  "direct list initialization of a lambda init-capture will change meaning in "
+  "a future version of Clang; insert an '=' to avoid a change in behavior">,
+  InGroup<FutureCompat>;
 
 // Availability attribute
 def err_expected_version : Error<
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 2afe77055b..b173d82a31 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1635,6 +1635,10 @@ def err_auto_var_init_multiple_expressions : Error<
 def err_auto_var_init_paren_braces : Error<
   "cannot deduce type for variable %0 with type %1 from "
   "parenthesized initializer list">;
+def warn_auto_var_direct_list_init : Warning<
+  "direct list initialization of a variable with a deduced type will change "
+  "meaning in a future version of Clang; insert an '=' to avoid a change in "
+  "behavior">, InGroup<FutureCompat>;
 def err_auto_new_ctor_multiple_expressions : Error<
   "new expression for type %0 contains multiple constructor arguments">;
 def err_auto_missing_trailing_return : Error<
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 355503caa9..67496edf8c 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -894,11 +894,16 @@ Optional<unsigned> Parser::ParseLambdaIntroducer(LambdaIntroducer &Intro,
         // to save the necessary state, and restore it later.
         EnterExpressionEvaluationContext EC(Actions,
                                             Sema::PotentiallyEvaluated);
-        TryConsumeToken(tok::equal);
+        bool HadEquals = TryConsumeToken(tok::equal);
 
-        if (!SkippedInits)
+        if (!SkippedInits) {
+          // Warn on constructs that will change meaning when we implement N3922
+          if (!HadEquals && Tok.is(tok::l_brace)) {
+            Diag(Tok, diag::warn_init_capture_direct_list_init)
+              << FixItHint::CreateInsertion(Tok.getLocation(), "=");
+          }
           Init = ParseInitializer();
-        else if (Tok.is(tok::l_brace)) {
+        } else if (Tok.is(tok::l_brace)) {
           BalancedDelimiterTracker Braces(*this, tok::l_brace);
           Braces.consumeOpen();
           Braces.skipToEnd();
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index b556f18b76..c6af2edee5 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -8702,6 +8702,14 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
     CheckVariableDeclarationType(VDecl);
     if (VDecl->isInvalidDecl())
       return;
+
+    // If all looks well, warn if this is a case that will change meaning when
+    // we implement N3922.
+    if (DirectInit && !CXXDirectInit && isa<InitListExpr>(Init)) {
+      Diag(Init->getLocStart(),
+           diag::warn_auto_var_direct_list_init)
+        << FixItHint::CreateInsertion(Init->getLocStart(), "=");
+    }
   }
 
   // dllimport cannot be used on variable definitions.
diff --git a/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp b/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
index 6be200dd54..1228c74b07 100644
--- a/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
+++ b/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
@@ -48,7 +48,7 @@ auto bad_init_2 = [a(1, 2)] {}; // expected-error {{initializer for lambda captu
 auto bad_init_3 = [&a(void_fn())] {}; // expected-error {{cannot form a reference to 'void'}}
 auto bad_init_4 = [a(void_fn())] {}; // expected-error {{has incomplete type 'void'}}
 auto bad_init_5 = [a(overload_fn)] {}; // expected-error {{cannot deduce type for lambda capture 'a' from initializer of type '<overloaded function}}
-auto bad_init_6 = [a{overload_fn}] {}; // expected-error {{cannot deduce type for lambda capture 'a' from initializer list}}
+auto bad_init_6 = [a{overload_fn}] {}; // expected-error {{cannot deduce type for lambda capture 'a' from initializer list}} expected-warning {{will change meaning in a future version of Clang}}
 
 template<typename...T> void pack_1(T...t) { (void)[a(t...)] {}; } // expected-error {{initializer missing for lambda capture 'a'}}
 template void pack_1<>(); // expected-note {{instantiation of}}
@@ -61,7 +61,7 @@ auto a = [a(4), b = 5, &c = static_cast<const int&&>(0)] {
   using T = decltype(c);
   using T = const int &;
 };
-auto b = [a{0}] {}; // expected-error {{include <initializer_list>}}
+auto b = [a{0}] {}; // expected-error {{include <initializer_list>}} expected-warning {{will change meaning in a future version of Clang}}
 
 struct S { S(); S(S&&); };
 template<typename T> struct remove_reference { typedef T type; };
diff --git a/test/Parser/cxx0x-lambda-expressions.cpp b/test/Parser/cxx0x-lambda-expressions.cpp
index 6f69d8096e..c2bf6fd396 100644
--- a/test/Parser/cxx0x-lambda-expressions.cpp
+++ b/test/Parser/cxx0x-lambda-expressions.cpp
@@ -61,7 +61,7 @@ class C {
   int z;
   void init_capture() {
     [n(0)] () mutable -> int { return ++n; }; // expected-warning{{extension}}
-    [n{0}] { return; }; // expected-error {{<initializer_list>}} expected-warning{{extension}}
+    [n{0}] { return; }; // expected-error {{<initializer_list>}} expected-warning{{extension}} expected-warning{{will change meaning in a future version}}
     [n = 0] { return ++n; }; // expected-error {{captured by copy in a non-mutable}} expected-warning{{extension}}
     [n = {0}] { return; }; // expected-error {{<initializer_list>}} expected-warning{{extension}}
     [a([&b = z]{})](){}; // expected-warning 2{{extension}}
diff --git a/test/Parser/objcxx0x-lambda-expressions.mm b/test/Parser/objcxx0x-lambda-expressions.mm
index bef576a9d2..3954a807a5 100644
--- a/test/Parser/objcxx0x-lambda-expressions.mm
+++ b/test/Parser/objcxx0x-lambda-expressions.mm
@@ -21,7 +21,7 @@ class C {
 
     [foo(bar)] () {};
     [foo = bar] () {};
-    [foo{bar}] () {}; // expected-error {{<initializer_list>}}
+    [foo{bar}] () {}; // expected-error {{<initializer_list>}} expected-warning {{will change meaning}}
     [foo = {bar}] () {}; // expected-error {{<initializer_list>}}
 
     [foo(bar) baz] () {}; // expected-error {{called object type 'int' is not a function}}
diff --git a/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp b/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
index 70f7c642a5..2405d2afe3 100644
--- a/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
+++ b/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
@@ -117,6 +117,7 @@ void argument_deduction() {
 
 void auto_deduction() {
   auto l = {1, 2, 3, 4};
+  auto l2 {1, 2, 3, 4}; // expected-warning {{will change meaning in a future version of Clang}}
   static_assert(same_type<decltype(l), std::initializer_list<int>>::value, "");
   auto bl = {1, 2.0}; // expected-error {{cannot deduce}}