[polly] [clang] [clang-format] Add AllowShortType option for AlwaysBreakAfterReturnType. (PR #78011)

[Owen Pan via cfe-commits]

owenca wrote:

Let's leave `None` alone and add `ExceptShortType`, e.g.:
```
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -329,12 +329,18 @@ bool ContinuationIndenter::canBreak(const LineState &State) {
   // Don't break after very short return types (e.g. "void") as that is often
   // unexpected.
   if (Current.is(TT_FunctionDeclarationName) && State.Column < 6) {
     if (Style.AlwaysBreakAfterReturnType == FormatStyle::RTBS_None)
       return false;
   }
+  if (Current.is(TT_FunctionDeclarationName) &&
+      Style.AlwaysBreakAfterReturnType == FormatStyle::RTBS_ExceptShortType) {
+    assert(State.Column >= State.FirstIndent);
+    if (State.Column - State.FirstIndent < 6)
+      return false;
+  }
 
   // If binary operators are moved to the next line (including commas for some
   // styles of constructor initializers), that's always ok.
   if (!Current.isOneOf(TT_BinaryOperator, tok::comma) &&
       // Allow breaking opening brace of lambdas (when passed as function
       // arguments) to a new line when BeforeLambdaBody brace wrapping is
```

https://github.com/llvm/llvm-project/pull/78011