[C++1z] Implement N3928: message in static_assert is optional.

llvm-svn: 211394

5 files changed, 41 insertions, 21 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index f7f08fc4cbb..035a7377e18 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -931,7 +931,12 @@ def warning_multiple_selectors: Warning<
 // C++ declarations
 def err_static_assert_expression_is_not_constant : Error<
   "static_assert expression is not an integral constant expression">;
-def err_static_assert_failed : Error<"static_assert failed %0">;
+def err_static_assert_failed : Error<"static_assert failed%select{ %1|}0">;
+def ext_static_assert_no_message : ExtWarn<
+  "static_assert with no message is a C++1z extension">, InGroup<CXX1z>;
+def warn_cxx1y_compat_static_assert_no_message : Warning<
+  "static_assert with no message is incompatible with C++ standards before C++1z">,
+  DefaultIgnore, InGroup<CXXPre1zCompat>;
 
 def warn_inline_namespace_reopened_noninline : Warning<
   "inline namespace cannot be reopened as a non-inline namespace">;
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 33e3cab8671..cd2e3971884 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -689,22 +689,32 @@ Decl *Parser::ParseStaticAssertDeclaration(SourceLocation &DeclEnd){
     return nullptr;
   }
 
-  if (ExpectAndConsume(tok::comma)) {
-    SkipUntil(tok::semi);
-    return nullptr;
-  }
+  ExprResult AssertMessage;
+  if (Tok.is(tok::r_paren)) {
+    Diag(Tok, getLangOpts().CPlusPlus1z
+                  ? diag::warn_cxx1y_compat_static_assert_no_message
+                  : diag::ext_static_assert_no_message)
+      << (getLangOpts().CPlusPlus1z
+              ? FixItHint()
+              : FixItHint::CreateInsertion(Tok.getLocation(), ", \"\""));
+  } else {
+    if (ExpectAndConsume(tok::comma)) {
+      SkipUntil(tok::semi);
+      return nullptr;
+    }
 
-  if (!isTokenStringLiteral()) {
-    Diag(Tok, diag::err_expected_string_literal)
-      << /*Source='static_assert'*/1;
-    SkipMalformedDecl();
-    return nullptr;
-  }
+    if (!isTokenStringLiteral()) {
+      Diag(Tok, diag::err_expected_string_literal)
+        << /*Source='static_assert'*/1;
+      SkipMalformedDecl();
+      return nullptr;
+    }
 
-  ExprResult AssertMessage(ParseStringLiteralExpression());
-  if (AssertMessage.isInvalid()) {
-    SkipMalformedDecl();
-    return nullptr;
+    AssertMessage = ParseStringLiteralExpression();
+    if (AssertMessage.isInvalid()) {
+      SkipMalformedDecl();
+      return nullptr;
+    }
   }
 
   T.consumeClose();
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 85394bb4de7..5ca53b0a08a 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -11405,7 +11405,8 @@ Decl *Sema::ActOnStaticAssertDeclaration(SourceLocation StaticAssertLoc,
                                          Expr *AssertExpr,
                                          Expr *AssertMessageExpr,
                                          SourceLocation RParenLoc) {
-  StringLiteral *AssertMessage = cast<StringLiteral>(AssertMessageExpr);
+  StringLiteral *AssertMessage =
+      AssertMessageExpr ? cast<StringLiteral>(AssertMessageExpr) : nullptr;
 
   if (DiagnoseUnexpandedParameterPack(AssertExpr, UPPC_StaticAssertExpression))
     return nullptr;
@@ -11419,8 +11420,7 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc,
                                          StringLiteral *AssertMessage,
                                          SourceLocation RParenLoc,
                                          bool Failed) {
-  assert(AssertExpr != nullptr && AssertMessage != nullptr &&
-         "Expected non-null Expr's");
+  assert(AssertExpr != nullptr && "Expected non-null condition");
   if (!AssertExpr->isTypeDependent() && !AssertExpr->isValueDependent() &&
       !Failed) {
     // In a static_assert-declaration, the constant-expression shall be a
@@ -11438,9 +11438,10 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc,
     if (!Failed && !Cond) {
       SmallString<256> MsgBuffer;
       llvm::raw_svector_ostream Msg(MsgBuffer);
-      AssertMessage->printPretty(Msg, nullptr, getPrintingPolicy());
+      if (AssertMessage)
+        AssertMessage->printPretty(Msg, nullptr, getPrintingPolicy());
       Diag(StaticAssertLoc, diag::err_static_assert_failed)
-        << Msg.str() << AssertExpr->getSourceRange();
+        << !AssertMessage << Msg.str() << AssertExpr->getSourceRange();
       Failed = true;
     }
   }
diff --git a/clang/test/SemaCXX/cxx0x-compat.cpp b/clang/test/SemaCXX/cxx0x-compat.cpp
index ffbd20fda37..a58a7f875cd 100644
--- a/clang/test/SemaCXX/cxx0x-compat.cpp
+++ b/clang/test/SemaCXX/cxx0x-compat.cpp
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -std=c++98 -Wc++11-compat -verify %s
-// RUN: %clang_cc1 -fsyntax-only -std=c++1y -Wc++11-compat -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++1z -Wc++11-compat -verify %s
 
 #if __cplusplus < 201103L
 
@@ -44,5 +44,6 @@ char c = 'x'_x; // expected-warning {{will be treated as a user-defined literal
 #else
 
 auto init_capture = [a(0)] {}; // expected-warning {{initialized lambda captures are incompatible with C++ standards before C++1y}}
+static_assert(true); // expected-warning {{incompatible with C++ standards before C++1z}}
 
 #endif
diff --git a/clang/test/SemaCXX/static-assert.cpp b/clang/test/SemaCXX/static-assert.cpp
index 4a7560ba5b6..c9d93843536 100644
--- a/clang/test/SemaCXX/static-assert.cpp
+++ b/clang/test/SemaCXX/static-assert.cpp
@@ -48,3 +48,6 @@ template<typename T> struct StaticAssertProtected {
 struct X { ~X(); };
 StaticAssertProtected<int> sap1;
 StaticAssertProtected<X> sap2; // expected-note {{instantiation}}
+
+static_assert(true); // expected-warning {{C++1z extension}}
+static_assert(false); // expected-error-re {{failed$}} expected-warning {{extension}}