Diagnose incorrect syntax for #pragma clang diagnostic

We would previously fail to diagnose unexpected tokens after a 'push'
or 'pop' directive.

Fixes #13920

Author: AaronBallman

clang/docs/ReleaseNotes.rst

@@ -366,6 +366,9 @@ Improvements to Clang's diagnostics
   been fixed and the Fix-It now only spans to the end of the ``:``.
 - Clang now underlines the parameter list of function declaration when emitting
   a note about the mismatch in the number of arguments.
+- Clang now diagnoses unexpected tokens after a
+  ``#pragma clang|GCC diagnostic push|pop`` directive.
+  (`#13920: <https://github.com/llvm/llvm-project/issues/13920>`_)
 
 Bug Fixes in This Version
 -------------------------

clang/lib/Lex/Pragma.cpp

@@ -1291,16 +1291,26 @@ struct PragmaDiagnosticHandler : public PragmaHandler {
     IdentifierInfo *II = Tok.getIdentifierInfo();
     PPCallbacks *Callbacks = PP.getPPCallbacks();
 
+    // Get the next token, which is either an EOD or a string literal. We lex
+    // it now so that we can early return if the previous token was push or pop.
+    PP.LexUnexpandedToken(Tok);
+
     if (II->isStr("pop")) {
       if (!PP.getDiagnostics().popMappings(DiagLoc))
         PP.Diag(Tok, diag::warn_pragma_diagnostic_cannot_pop);
       else if (Callbacks)
         Callbacks->PragmaDiagnosticPop(DiagLoc, Namespace);
+
+      if (Tok.isNot(tok::eod))
+        PP.Diag(Tok.getLocation(), diag::warn_pragma_diagnostic_invalid_token);
       return;
     } else if (II->isStr("push")) {
       PP.getDiagnostics().pushMappings(DiagLoc);
       if (Callbacks)
         Callbacks->PragmaDiagnosticPush(DiagLoc, Namespace);
+
+      if (Tok.isNot(tok::eod))
+        PP.Diag(Tok.getLocation(), diag::warn_pragma_diagnostic_invalid_token);
       return;
     }
 
@@ -1316,9 +1326,8 @@ struct PragmaDiagnosticHandler : public PragmaHandler {
       return;
     }
 
-    PP.LexUnexpandedToken(Tok);
+    // At this point, we expect a string literal.
     SourceLocation StringLoc = Tok.getLocation();
-
     std::string WarningName;
     if (!PP.FinishLexStringLiteral(Tok, WarningName, "pragma diagnostic",
                                    /*AllowMacroExpansion=*/false))

clang/test/Preprocessor/pragma_diagnostic.c

@@ -34,6 +34,11 @@
 // expected-warning@-2 {{unknown warning group '-Winvalid-name', ignored}}
 #endif
 
+// From GH13920
+#pragma clang diagnostic push ignored "-Wdeprecated-declarations" // expected-warning {{unexpected token in pragma diagnostic}}
+#pragma clang diagnostic pop ignored "-Wdeprecated-declarations"  // expected-warning {{unexpected token in pragma diagnostic}}
+
+
 // Testing pragma clang diagnostic with -Weverything
 void ppo(void){} // First test that we do not diagnose on this.