DiagnosticVerifier: Support line offsets in fix-it verification ranges

[AnthonyLatsis]

Follow-up to #39572

The range syntax is now ([+-]?N:)?N-([+-]?N:)?N where N is [0-9]+.

[AnthonyLatsis]

@swift-ci please smoke test

[rintaro]

Thank you! Just a few comments about code styling. Implementation looks pretty good

[rintaro]

This is a little bit confusing. I feel std::make_pair(LineColumnRange::NoValue, firstValue) is more clear.

[rintaro]

auto lineNo = DiagnosticLineNo;
switch (lineOffsetKind) {
case ::None
  lineNo = firstValue;
  break;
case ::Plus
  lineNo += firstValue;
  break;
case ::Minus
  lineNo -= firstValue;
  break;
}

WDYT?

[rintaro]

Clever, but

  const enum class LineOffsetKind : uint8_t {
    None,
    Plus,
    Minus
  };

  LineOffsetKind lineOffsetKind = LineOffsetKind::None;
  switch (Str.front()) {
  case '+':
    lineOffsetKind = LineOffsetKind::Plus;
    Str = Str.drop_front();
    break;
  case '-':
    lineOffsetKind = LineOffsetKind::Minus;
    Str = Str.drop_front();
    break;
  default:
    break;
  } 

feels easier to read.

[AnthonyLatsis]

I had the feeling this was gonna bug someone 😄

No problem, can I keep the lambda for constness though? When reading C++, I feel a ton of relief every time I see that something's not going to be mutated in the next 50+ lines.

[AnthonyLatsis]

Actually, never mind; the difference looks negligible this time.

[rintaro]

@swift-ci Please smoke test

[AnthonyLatsis]

@rintaro Appreciate the review!