[Parser] Emit descriptive diagnostic for misplaced pragma

[sepavloff]

Summary

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.

[sepavloff]

Ping.

[rjmccall]

clang/lib/Basic/TokenKinds.cpp

55 ↗

(On Diff #210610)

The right way to do this is to make a PRAGMA_ANNOTATION macro in TokenKinds.def that defaults to ANNOTATION, like that file already does with e.g. CXX11_KEYWORD. But for future reference, there's also a StringRef::startsWith.

[sepavloff]

Updated patch

Move logically independent changes to separate patches.

[rjmccall]

clang/lib/Basic/TokenKinds.cpp

15 ↗

(On Diff #212188)

This is no longer necessary, right?

[sepavloff]

Updated patch

[sepavloff]

clang/lib/Basic/TokenKinds.cpp

15 ↗

(On Diff #212188)

Sure, removed it.

[rjmccall]

LGTM

clang/include/clang/Basic/DiagnosticParseKinds.td

def warn_pragma_expected_identifier : Warning<
   "expected identifier in '#pragma %0' - ignored">, InGroup<IgnoredPragmas>;
 def warn_pragma_expected_string : Warning<
   "expected string literal in '#pragma %0' - ignoring">, InGroup<IgnoredPragmas>;
 def warn_pragma_missing_argument : Warning<
   "missing argument to '#pragma %0'%select{|; expected %2}1">, InGroup<IgnoredPragmas>;
 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'">;
 def err_pragma_clang_section_expected_equal : Error<
   "expected '=' following '#pragma clang section %select{invalid|bss|data|rodata|text}0'">;
 def warn_pragma_expected_section_name : Warning<
   "expected a string literal for the section name in '#pragma %0' - ignored">,
   InGroup<IgnoredPragmas>;

clang/lib/Parse/ParseDecl.cpp

while (!tryParseMisplacedModuleImport() && Tok.isNot(tok::r_brace) &&
     if (Tok.is(tok::annot_pragma_openmp)) {
       // Result can be ignored, because it must be always empty.
       AccessSpecifier AS = AS_none;
       ParsedAttributesWithRange Attrs(AttrFactory);
       (void)ParseOpenMPDeclarativeDirectiveWithExtDecl(AS, Attrs);
       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.
         Decl *Field =
             Actions.ActOnField(getCurScope(), TagDecl,
                                FD.D.getDeclSpec().getSourceRange().getBegin(),
                                FD.D, FD.BitfieldSize);
         FieldDecls.push_back(Field);

clang/lib/Parse/ParseDeclCXX.cpp

case tok::kw_protected: {
     return nullptr;
   }
 
   case tok::annot_pragma_openmp:
     return ParseOpenMPDeclarativeDirectiveWithExtDecl(AS, AccessAttrs, TagType,
                                                       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);
   }
 }
 
 /// ParseCXXMemberSpecification - Parse the class definition.
 ///
 ///       member-specification:
 ///         member-declaration member-specification[opt]

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

 }
 
 int a = f(); // expected-warning{{'f' is only available on macOS 1000 or newer}} expected-note{{annotate 'a'}}
 int b = my_ns::g(); // expected-warning{{'g' is only available on macOS 1000 or newer}} expected-note{{annotate 'b'}}
 int c = my_ns::nested::h(); // expected-warning{{'h' is only available on macOS 1000 or newer}} expected-note{{annotate 'c'}}
 
 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

 // 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
+};

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

+// 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;
+};