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

[Owen Pan via cfe-commits]

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@@ -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);
 }
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owenca wrote:

> The fix I would originally do was just look behind again and see if the ) belongs to a decltype, I just also tried removing the case entirely, and was surprised it works. If you prefer, I can follow my original plan and add an extra check for decltype

In general, I prefer to not include code that can't be reached by test cases as the code is likely superfluous. Because @HazardyKnusperkeks is ok with its removal, wouldn't be better to just do that?

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