Revert "Merge pull request swiftlang#9200 from compnerd/static_assert_false"

This reverts commit 4857f75, reversing
changes made to fe0f467.

This reverts PR swiftlang#9200.

The cherry-pick that's being tried in that PR is already part of the
branch (00e2098), and the commit removes code added after the original
commit, and duplicates some testing code, producing errors in several
tests.

See the comments of swiftlang#9200 for more details.

Author: drodriguez

clang/lib/Sema/SemaDeclCXX.cpp

@@ -17146,14 +17146,21 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc,
                        FoldKind).isInvalid())
       Failed = true;
 
+    // If the static_assert passes, only verify that
+    // the message is grammatically valid without evaluating it.
+    if (!Failed && AssertMessage && Cond.getBoolValue()) {
+      std::string Str;
+      EvaluateStaticAssertMessageAsString(AssertMessage, Str, Context,
+                                          /*ErrorOnInvalidMessage=*/false);
+    }
+
     // CWG2518
     // [dcl.pre]/p10  If [...] the expression is evaluated in the context of a
     // template definition, the declaration has no effect.
     bool InTemplateDefinition =
         getLangOpts().CPlusPlus && CurContext->isDependentContext();
 
     if (!Failed && !Cond && !InTemplateDefinition) {
-
       SmallString<256> MsgBuffer;
       llvm::raw_svector_ostream Msg(MsgBuffer);
       bool HasMessage = AssertMessage;
@@ -17185,8 +17192,8 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc,
             << InnerCond->getSourceRange();
         DiagnoseStaticAssertDetails(InnerCond);
       } else {
-        Diag(StaticAssertLoc, diag::err_static_assert_failed)
-            << !AssertMessage << Msg.str() << AssertExpr->getSourceRange();
+        Diag(AssertExpr->getBeginLoc(), diag::err_static_assert_failed)
+            << !HasMessage << Msg.str() << AssertExpr->getSourceRange();
         PrintContextStack();
       }
       Failed = true;

clang/test/CXX/drs/dr25xx.cpp

@@ -81,40 +81,6 @@ using ::dr2521::operator""_div;
 #endif
 } // namespace dr2521
 
-namespace dr2518 { // dr2518: 17 review
-
-template <class T>
-void f(T t) {
-  if constexpr (sizeof(T) != sizeof(int)) {
-    static_assert(false, "must be int-sized"); // expected-error {{must be int-size}}
-  }
-}
-
-void g(char c) {
-  f(0);
-  f(c); // expected-note {{requested here}}
-}
-
-template <typename Ty>
-struct S {
-  static_assert(false); // expected-error {{static assertion failed}}
-};
-
-template <>
-struct S<int> {};
-
-template <>
-struct S<float> {};
-
-int test_specialization() {
-  S<int> s1;
-  S<float> s2;
-  S<double> s3; // expected-note {{in instantiation of template class 'dr2518::S<double>' requested here}}
-}
-
-}
-
-
 namespace dr2565 { // dr2565: 16 open
 #if __cplusplus >= 202002L
   template<typename T>