[Parser] Emit descriptive diagnostic for misplaced pragma

If a class or struct or union declaration contains a pragma that
is not valid in this context, compiler issues generic error like
"expected member name or ';' after declaration specifiers". With this
change the error tells that this pragma cannot appear in this declaration.

Differential Revision: https://reviews.llvm.org/D64932

llvm-svn: 367779

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -974,6 +974,8 @@ def warn_pragma_missing_argument : Warning<
 def warn_pragma_invalid_argument : Warning<
   "unexpected argument '%0' to '#pragma %1'%select{|; expected %3}2">, InGroup<IgnoredPragmas>;
 
+def err_pragma_misplaced_in_decl : Error<"this pragma cannot appear in %0 declaration">;
+
 // '#pragma clang section' related errors
 def err_pragma_expected_clang_section_name : Error<
   "expected one of [bss|data|rodata|text] section kind in '#pragma %0'">;

clang/lib/Parse/ParseDecl.cpp

@@ -4148,6 +4148,14 @@ void Parser::ParseStructUnionBody(SourceLocation RecordLoc,
       continue;
     }
 
+    if (tok::isPragmaAnnotation(Tok.getKind())) {
+      Diag(Tok.getLocation(), diag::err_pragma_misplaced_in_decl)
+          << DeclSpec::getSpecifierName(
+                 TagType, Actions.getASTContext().getPrintingPolicy());
+      ConsumeAnnotationToken();
+      continue;
+    }
+
     if (!Tok.is(tok::at)) {
       auto CFieldCallback = [&](ParsingFieldDeclarator &FD) {
         // Install the declarator into the current TagDecl.

clang/lib/Parse/ParseDeclCXX.cpp

@@ -3134,6 +3134,13 @@ Parser::DeclGroupPtrTy Parser::ParseCXXClassMemberDeclarationWithPragmas(
                                                       TagDecl);
 
   default:
+    if (tok::isPragmaAnnotation(Tok.getKind())) {
+      Diag(Tok.getLocation(), diag::err_pragma_misplaced_in_decl)
+          << DeclSpec::getSpecifierName(TagType,
+                                   Actions.getASTContext().getPrintingPolicy());
+      ConsumeAnnotationToken();
+      return nullptr;
+    }
     return ParseCXXClassMemberDeclaration(AS, AccessAttrs);
   }
 }

clang/test/Parser/pragma-attribute-context.cpp

@@ -31,8 +31,7 @@ int c = my_ns::nested::h(); // expected-warning{{'h' is only available on macOS
 
 struct InStruct {
   // FIXME: This asserts in Objective-C++!
-  // FIXME: This is a horrible diagnostic!
 #ifndef __OBJC__
-  BEGIN_PRAGMA // expected-error {{expected member name or ';' after declaration specifiers}}
+  BEGIN_PRAGMA // expected-error {{this pragma cannot appear in struct declaration}}
 #endif
 };

clang/test/Parser/pragma-fp-contract.c

@@ -10,3 +10,16 @@ void f2(void) {
   #pragma STDC FP_CONTRACT OFF
   #pragma STDC FP_CONTRACT ON 
 }
+
+struct S1 {
+// expected-error@+1 {{this pragma cannot appear in struct declaration}}
+#pragma STDC FP_CONTRACT ON
+  float f1;
+};
+
+union U1 {
+  float f1;
+  float f2;
+// expected-error@+1 {{this pragma cannot appear in union declaration}}
+#pragma STDC FP_CONTRACT ON
+};

clang/test/Parser/pragma-fp-contract.cpp

@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void f1(void) {
+  int x = 0;
+/* expected-error@+1 {{'#pragma fp_contract' can only appear at file scope or at the start of a compound statement}} */
+#pragma STDC FP_CONTRACT ON
+}
+
+void f2(void) {
+  #pragma STDC FP_CONTRACT OFF
+  #pragma STDC FP_CONTRACT ON
+}
+
+struct S1 {
+// expected-error@+1 {{this pragma cannot appear in struct declaration}}
+#pragma STDC FP_CONTRACT ON
+  float f1;
+};
+
+union U1 {
+  float f1;
+  float f2;
+// expected-error@+1 {{this pragma cannot appear in union declaration}}
+#pragma STDC FP_CONTRACT ON
+};
+
+class C1 {
+  float f1;
+// expected-error@+1 {{this pragma cannot appear in class declaration}}
+#pragma STDC FP_CONTRACT ON
+  float f2;
+};