[clang] [clang-format] Fix misannotations of `<` in ternary expressions (PR #100980)

[Emilia Kond via cfe-commits]

================
@@ -176,31 +176,38 @@ class AnnotatingParser {
     FormatToken *Left = CurrentToken->Previous;
     Left->ParentBracket = Contexts.back().ContextKind;
     ScopedContextCreator ContextCreator(*this, tok::less, 12);
-
     Contexts.back().IsExpression = false;
+
+    const auto *BeforeLess = Left->Previous;
+
     // If there's a template keyword before the opening angle bracket, this is a
     // template parameter, not an argument.
-    if (Left->Previous && Left->Previous->isNot(tok::kw_template))
+    if (BeforeLess && BeforeLess->isNot(tok::kw_template))
       Contexts.back().ContextType = Context::TemplateArgument;
 
     if (Style.Language == FormatStyle::LK_Java &&
         CurrentToken->is(tok::question)) {
       next();
     }
 
-    while (CurrentToken) {
+    for (bool SeenTernaryOperator = false; CurrentToken;) {
+      const bool InExpr = Contexts[Contexts.size() - 2].IsExpression;
       if (CurrentToken->is(tok::greater)) {
+        const auto *Next = CurrentToken->Next;
         // Try to do a better job at looking for ">>" within the condition of
         // a statement. Conservatively insert spaces between consecutive ">"
         // tokens to prevent splitting right bitshift operators and potentially
         // altering program semantics. This check is overly conservative and
         // will prevent spaces from being inserted in select nested template
         // parameter cases, but should not alter program semantics.
-        if (CurrentToken->Next && CurrentToken->Next->is(tok::greater) &&
+        if (Next && Next->is(tok::greater) &&
             Left->ParentBracket != tok::less &&
             CurrentToken->getStartOfNonWhitespace() ==
-                CurrentToken->Next->getStartOfNonWhitespace().getLocWithOffset(
-                    -1)) {
+                Next->getStartOfNonWhitespace().getLocWithOffset(-1)) {
+          return false;
+        }
+        if (InExpr && SeenTernaryOperator &&
+            (!Next || Next->isNot(tok::l_paren))) {
----------------
rymiel wrote:

Maybe I'm looking too hard for edge-cases, but maybe we could also add l_brace here? This is valid code:

```c++
template <int I>
struct Foo {
    int i = I;
};

auto a = Foo<false ? 1 : 2>{};
```

https://github.com/llvm/llvm-project/pull/100980