[clang] Informative error for lifetimebound in decl-spec (#118567)

Emit a bit more informative error when the `[[clang::lifetimebound]]`
attribute is wrongly appearing on a decl-spec:

```
'lifetimebound' attribute only applies to parameters and implicit
object parameters
```

instead of:

```
'lifetimebound' attribute cannot be applied to types
```

The new error is also consistent with the diagnostic emitted when the
attribute is misplaced in other parts of a declarator.

Author: emaxx-google

clang/lib/Parse/ParseDecl.cpp

@@ -3706,8 +3706,14 @@ void Parser::ParseDeclarationSpecifiers(
           if (PA.isTypeAttr() && PA.getKind() != ParsedAttr::AT_LifetimeBound &&
               PA.getKind() != ParsedAttr::AT_AnyX86NoCfCheck)
             continue;
-          Diag(PA.getLoc(), diag::err_attribute_not_type_attr)
-              << PA << PA.isRegularKeywordAttribute();
+
+          if (PA.getKind() == ParsedAttr::AT_LifetimeBound)
+            Diag(PA.getLoc(), diag::err_attribute_wrong_decl_type_str)
+                << PA << PA.isRegularKeywordAttribute()
+                << "parameters and implicit object parameters";
+          else
+            Diag(PA.getLoc(), diag::err_attribute_not_type_attr)
+                << PA << PA.isRegularKeywordAttribute();
           PA.setInvalid();
         }
 

clang/test/SemaCXX/attr-lifetimebound.cpp

@@ -10,7 +10,7 @@ namespace usage_invalid {
     static int *static_class_member() [[clang::lifetimebound]]; // expected-error {{static member function has no implicit object parameter}}
     int *explicit_object(this A&) [[clang::lifetimebound]]; // expected-error {{explicit object member function has no implicit object parameter}}
     int attr_on_var [[clang::lifetimebound]]; // expected-error {{only applies to parameters and implicit object parameters}}
-    int [[clang::lifetimebound]] attr_on_int; // expected-error {{cannot be applied to types}}
+    int [[clang::lifetimebound]] attr_on_int; // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
     int * [[clang::lifetimebound]] attr_on_int_ptr; // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
     int * [[clang::lifetimebound]] * attr_on_int_ptr_ptr; // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
     int (* [[clang::lifetimebound]] attr_on_func_ptr)(); // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
@@ -19,7 +19,7 @@ namespace usage_invalid {
   int *attr_with_param(int &param [[clang::lifetimebound(42)]]); // expected-error {{takes no arguments}}
 
   void attr_on_ptr_arg(int * [[clang::lifetimebound]] ptr); // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
-  static_assert((int [[clang::lifetimebound]]) 12); // expected-error {{cannot be applied to types}}
+  static_assert((int [[clang::lifetimebound]]) 12); // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
   int* attr_on_unnamed_arg(const int& [[clang::lifetimebound]]); // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}
   template <typename T>
   int* attr_on_template_ptr_arg(T * [[clang::lifetimebound]] ptr); // expected-error {{'lifetimebound' attribute only applies to parameters and implicit object parameters}}