[clang-format] Disallow requires clauses to become function declarations

[rymiel]

Summary

There already exists logic to disallow requires *expressions* to be
treated as function declarations, but this expands it to include
requires *clauses*, when they happen to also be parenthesized.

Previously, in the following case:

template <typename T>
  requires(Foo<T>)
T foo();

The line with the requires clause was actually being considered as the
line with the function declaration due to the parentheses, and the
*real* function declaration on the next line became a trailing
annotation

(Together with https://reviews.llvm.org/D134049) Fixes https://github.com/llvm/llvm-project/issues/56213

clang/lib/Format/TokenAnnotator.cpp

case tok::l_paren:
       }
 
       if (!parseParens())
         return false;
       if (Line.MustBeDeclaration && Contexts.size() == 1 &&
           !Contexts.back().IsExpression && !Line.startsWith(TT_ObjCProperty) &&
           !Tok->isOneOf(TT_TypeDeclarationParen, TT_RequiresExpressionLParen) &&
           (!Tok->Previous ||
-           !Tok->Previous->isOneOf(tok::kw___attribute,
+           !Tok->Previous->isOneOf(tok::kw___attribute, TT_RequiresClause,
                                    TT_LeadingJavaAnnotation))) {
         Line.MightBeFunctionDecl = true;
       }
       break;
     case tok::l_square:
       if (!parseSquare())
         return false;
       break;

clang/unittests/Format/TokenAnnotatorTest.cpp

ConstrainedCode = "template<typename T>\n"
                     "T foo() requires Foo<T> {\n"
                     "  auto bar = baz();\n"
                     "  return bar + T{};\n"
                     "}";
   BaseTokenCount = 26;
   TestRequires(__LINE__);
 
   BaseCode = "template<typename T>\n"
+             "T foo();";
+  ConstrainedCode = "template<typename T>\n"
+                    "  requires(Foo<T>)\n"
+                    "T foo();";
+  BaseTokenCount = 11;
+  RequiresTokenCount = 7;
+  PrefixTokenCount = 5;
+  TestRequires(__LINE__);
+
+  BaseCode = "template<typename T>\n"
              "Bar(T) -> Bar<typename T::I>;";
   ConstrainedCode = "template<typename T>\n"
                     "  requires requires(T &&t) {\n"
                     "             typename T::I;\n"
                     "           }\n"
                     "Bar(T) -> Bar<typename T::I>;";
   BaseTokenCount = 19;
   RequiresTokenCount = 14;