[clang-format] Fix a crash on lambda trailing return type

[owenpan]

Summary

Fixes https://github.com/llvm/llvm-project/issues/55625.

[curdeius]

LGTM. It seems it has landed already.

[owenpan]

In D126132#3530076, @curdeius wrote:

LGTM. It seems it has landed already.

Yeah. I pushed it by mistake. :(

[MyDeveloperDay]

LGTM (sorry I've been slow on the reviews, my day job keeps getting in the way ;-))

[curdeius]

Closing as it landed in https://github.com/llvm/llvm-project/commit/130a9cc0a5e25e3be8ff3738518e86ae3ae0b5ba.

[owenpan]

In D126132#3531643, @MyDeveloperDay wrote:

LGTM (sorry I've been slow on the reviews, my day job keeps getting in the way ;-))

Np! It's really that @curdeius and @HazardyKnusperkeks are fast. :)

clang/lib/Format/TokenAnnotator.cpp

1189

Ironically, I forgot to add the braces! This was caught and fixed by InsertBraces in D126157, though.

[owenpan]

@HazardyKnusperkeks I think you know this better than any of us as you added the assertion to setType(). Does this look ok to you?

[HazardyKnusperkeks]

In D126132#3533033, @owenpan wrote:

@HazardyKnusperkeks I think you know this better than any of us as you added the assertion to setType(). Does this look ok to you?

This looks good.
One should define what is the difference between TT_LambdaArrow and TT_TrailingReturnArrow. But if there is a difference, then the lambda arrows should stay TT_LambdaArrow, right?

In D126132#3531643, @MyDeveloperDay wrote:

LGTM (sorry I've been slow on the reviews, my day job keeps getting in the way ;-))

Same here, I'm just starting to catch up the last weeks. :)

[owenpan]

In D126132#3546767, @HazardyKnusperkeks wrote:

One should define what is the difference between TT_LambdaArrow and TT_TrailingReturnArrow. But if there is a difference, then the lambda arrows should stay TT_LambdaArrow, right?

It seems there is no difference. See https://github.com/llvm/llvm-project/pull/70519.

clang/lib/Format/TokenAnnotator.cpp

case tok::identifier:
         parseHasInclude();
       if (Style.isCSharp() && Tok->is(Keywords.kw_where) && Tok->Next &&
           Tok->Next->isNot(tok::l_paren)) {
         Tok->setType(TT_CSharpGenericTypeConstraint);
         parseCSharpGenericTypeConstraint();
       }
       break;
     case tok::arrow:
-      if (Tok->Previous && Tok->Previous->is(tok::kw_noexcept))
+      if (Tok->isNot(TT_LambdaArrow) && Tok->Previous &&
+          Tok->Previous->is(tok::kw_noexcept))
         Tok->setType(TT_TrailingReturnArrow);
       break;
     default:
       break;
     }
     return true;
   }
 

clang/unittests/Format/FormatTest.cpp

verifyFormat(
       "    std::function<bool()> bbbbbbbbbbbb = [&]() { return true; },\n"
       "    aaaaa aaaaaaaaa);");
 
   // Lambdas with return types.
   verifyFormat("int c = []() -> int { return 2; }();\n");
   verifyFormat("int c = []() -> int * { return 2; }();\n");
   verifyFormat("int c = []() -> vector<int> { return {2}; }();\n");
   verifyFormat("Foo([]() -> std::vector<int> { return {2}; }());");
+  verifyFormat("foo([]() noexcept -> int {});");
   verifyGoogleFormat("auto a = [&b, c](D* d) -> D* {};");
   verifyGoogleFormat("auto a = [&b, c](D* d) -> pair<D*, D*> {};");
   verifyGoogleFormat("auto a = [&b, c](D* d) -> D& {};");
   verifyGoogleFormat("auto a = [&b, c](D* d) -> const D* {};");
   verifyFormat("[a, a]() -> a<1> {};");
   verifyFormat("[]() -> foo<5 + 2> { return {}; };");
   verifyFormat("[]() -> foo<5 - 2> { return {}; };");
   verifyFormat("[]() -> foo<5 / 2> { return {}; };");