[clang] 1cbdf93 - PR46231: Promote diagnostic for 'template<...>;' from ExtWarn to Error.

[Richard Smith via cfe-commits]

Author: Richard Smith
Date: 2020-07-29T12:35:18-07:00
New Revision: 1cbdf932b41eb58ed94fbc240e93b63653d95bd3

URL: https://github.com/llvm/llvm-project/commit/1cbdf932b41eb58ed94fbc240e93b63653d95bd3
DIFF: https://github.com/llvm/llvm-project/commit/1cbdf932b41eb58ed94fbc240e93b63653d95bd3.diff

LOG: PR46231: Promote diagnostic for 'template<...>;' from ExtWarn to Error.

No other compiler accepts this as an extension, not even in permissive
mode. We're not doing anyone any favors by allowing this, and it's
unlikely to be at all common, even in Clang-only code, in the wild.

Added: 
    

Modified: 
    clang/include/clang/Basic/DiagnosticSemaKinds.td
    clang/lib/Sema/SemaDecl.cpp
    clang/test/Parser/cxx-template-decl.cpp
    clang/test/SemaCXX/PR16677.cpp
    clang/test/SemaCXX/invalid-template-params.cpp
    clang/test/SemaTemplate/template-decl-fail.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 794ef23f0761..91112860a2d0 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -793,6 +793,7 @@ def ext_main_used : Extension<
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
   InGroup<MissingDeclarations>;
+def err_no_declarators : Error<"declaration does not declare anything">;
 def ext_typedef_without_a_name : ExtWarn<"typedef requires a name">,
   InGroup<MissingDeclarations>;
 def err_typedef_not_identifier : Error<"typedef name must be an identifier">;

diff  --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ddbf086ea638..9b9d164dcbc1 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4766,7 +4766,10 @@ Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
   if (!DeclaresAnything) {
     // In C, we allow this as a (popular) extension / bug. Don't bother
     // producing further diagnostics for redundant qualifiers after this.
-    Diag(DS.getBeginLoc(), diag::ext_no_declarators) << DS.getSourceRange();
+    Diag(DS.getBeginLoc(), (IsExplicitInstantiation || !TemplateParams.empty())
+                               ? diag::err_no_declarators
+                               : diag::ext_no_declarators)
+        << DS.getSourceRange();
     return TagD;
   }
 

diff  --git a/clang/test/Parser/cxx-template-decl.cpp b/clang/test/Parser/cxx-template-decl.cpp
index 64e7ca921f57..7455b1d0ffe7 100644
--- a/clang/test/Parser/cxx-template-decl.cpp
+++ b/clang/test/Parser/cxx-template-decl.cpp
@@ -12,7 +12,7 @@ export template x;      // expected-error {{expected '<' after 'template'}}
 export template<class T> class x0; // expected-warning {{exported templates are unsupported}}
 template < ;            // expected-error {{expected template parameter}} \
 // expected-error{{expected ',' or '>' in template-parameter-list}} \
-// expected-warning {{declaration does not declare anything}}
+// expected-error {{declaration does not declare anything}}
 template <int +> struct x1; // expected-error {{expected ',' or '>' in template-parameter-list}}
 
 // verifies that we only walk to the ',' & still produce errors on the rest of the template parameters
@@ -286,3 +286,12 @@ namespace PR45239 {
   template<int> int b;
   template<int> auto f() -> b<0>; // expected-error +{{}}
 }
+
+namespace PR46231 {
+  template; // expected-error {{declaration does not declare anything}}
+  template<>; // expected-error {{declaration does not declare anything}}
+  template<int>; // expected-error {{declaration does not declare anything}}
+  template int; // expected-error {{declaration does not declare anything}}
+  template<> int; // expected-error {{declaration does not declare anything}}
+  template<int> int; // expected-error {{declaration does not declare anything}}
+}

diff  --git a/clang/test/SemaCXX/PR16677.cpp b/clang/test/SemaCXX/PR16677.cpp
index efa4faaacd69..3ad76c6d861d 100644
--- a/clang/test/SemaCXX/PR16677.cpp
+++ b/clang/test/SemaCXX/PR16677.cpp
@@ -11,5 +11,5 @@ template<class T,  // Should be angle bracket instead of comma
 class Derived : public Base<T> { // expected-error{{'Derived' cannot be defined in a type specifier}}
   Class_With_Destructor member;
 }; // expected-error{{expected ',' or '>' in template-parameter-list}}
-   // expected-warning at -1{{declaration does not declare anything}}
+   // expected-error at -1{{declaration does not declare anything}}
 

diff  --git a/clang/test/SemaCXX/invalid-template-params.cpp b/clang/test/SemaCXX/invalid-template-params.cpp
index 0c463fe13d5b..21220f3fea34 100644
--- a/clang/test/SemaCXX/invalid-template-params.cpp
+++ b/clang/test/SemaCXX/invalid-template-params.cpp
@@ -5,7 +5,7 @@ template<class> class Foo {
                       // expected-note at -1 {{'UBar' declared here}}
   void foo1(); // expected-error {{a non-type template parameter cannot have type 'class UBar'}}
                // expected-error at -1 {{expected ',' or '>' in template-parameter-list}}
-               // expected-warning at -2 {{declaration does not declare anything}}
+               // expected-error at -2 {{declaration does not declare anything}}
 };
 
 Foo<int>::UBar g1; // expected-error {{no type named 'UBar' in 'Foo<int>'}}
@@ -16,7 +16,7 @@ class C0 {
   struct S0 {}; // expected-error {{'S0' cannot be defined in a type specifier}}
                 // expected-error at -1 {{cannot combine with previous 'type-name' declaration specifier}}
                 // expected-error at -2 {{expected ',' or '>' in template-parameter-list}}
-                // expected-warning at -3 {{declaration does not declare anything}}
+                // expected-error at -3 {{declaration does not declare anything}}
   C0() : m(new S0<int>) {} // expected-error {{expected '(' for function-style cast or type construction}}
                            // expected-error at -1 {{expected expression}}
   S0<int> *m; // expected-error {{expected member name or ';' after declaration specifiers}}

diff  --git a/clang/test/SemaTemplate/template-decl-fail.cpp b/clang/test/SemaTemplate/template-decl-fail.cpp
index ad134cdf225c..7019caa2c2f3 100644
--- a/clang/test/SemaTemplate/template-decl-fail.cpp
+++ b/clang/test/SemaTemplate/template-decl-fail.cpp
@@ -4,7 +4,7 @@ template<typename T> typedef T X; // expected-error{{typedef cannot be a templat
 
 template<typename T>
 enum t0 { A = T::x }; // expected-error{{enumeration cannot be a template}} \
-                      // expected-warning{{declaration does not declare anything}}
+                      // expected-error{{declaration does not declare anything}}
 
 enum e0 {};
 template<int x> enum e0 f0(int a=x) {}