[clang] [clang-format] Allow decltype in requires clause (PR #78847)

[Björn Schäpers via cfe-commits]

================
@@ -1071,6 +1071,16 @@ TEST_F(TokenAnnotatorTest, UnderstandsRequiresClausesAndConcepts) {
                     "concept C = (!Foo<T>) && Bar;");
   ASSERT_EQ(Tokens.size(), 19u) << Tokens;
   EXPECT_TOKEN(Tokens[15], tok::ampamp, TT_BinaryOperator);
+
+  Tokens = annotate("void f() & requires(C<decltype(x)>) {}");
+  ASSERT_EQ(Tokens.size(), 18u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::amp, TT_PointerOrReference);
+  EXPECT_TOKEN(Tokens[5], tok::kw_requires, TT_RequiresClause);
+
+  Tokens = annotate("auto f() -> int& requires(C<decltype(x)>) {}");
+  ASSERT_EQ(Tokens.size(), 20u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::amp, TT_PointerOrReference);
+  EXPECT_TOKEN(Tokens[7], tok::kw_requires, TT_RequiresClause);
 }
----------------
HazardyKnusperkeks wrote:

I have no problem with removing it. If you keep it, I would add a check for `OpenAngles == 0`. The same applies to `||` because one could write something like
```c++
requires (T<C1 || C2> t) {}
```

So the whole logic should only apply to the out of template area, similar to `const`, `volatile`, and `comma` above.

https://github.com/llvm/llvm-project/pull/78847