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Minimize weird spans involving macro context

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Sometimes the parser attempts to synthesize spans from within a macro
context with the span for the captured argument, leading to non-sensical
spans with very bad output. Given that an incorrect span is worse than
a partially incomplete span, when detecting this situation return only
one of the spans without mergin them.
This commit is contained in:
Esteban Küber 2018-02-01 11:51:49 -08:00
parent bacb5c58df
commit aaec608367
4 changed files with 55 additions and 8 deletions
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23
src/libsyntax_pos/lib.rs
View file

@ -361,13 +361,24 @@ impl Span {
/// Return a `Span` that would enclose both `self` and `end`.
pub fn to(self, end: Span) -> Span {
let span = self.data();
let end = end.data();
let span_data = self.data();
let end_data = end.data();
// FIXME(jseyfried): self.ctxt should always equal end.ctxt here (c.f. issue #23480)
// Return the macro span on its own to avoid weird diagnostic output. It is preferable to
// have an incomplete span than a completely nonsensical one.
if span_data.ctxt != end_data.ctxt {
if span_data.ctxt == SyntaxContext::empty() {
return end;
} else if end_data.ctxt == SyntaxContext::empty() {
return self;
}
// both span fall within a macro
// FIXME(estebank) check if it is the *same* macro
}
Span::new(
cmp::min(span.lo, end.lo),
cmp::max(span.hi, end.hi),
// FIXME(jseyfried): self.ctxt should always equal end.ctxt here (c.f. issue #23480)
if span.ctxt == SyntaxContext::empty() { end.ctxt } else { span.ctxt },
cmp::min(span_data.lo, end_data.lo),
cmp::max(span_data.hi, end_data.hi),
if span_data.ctxt == SyntaxContext::empty() { end_data.ctxt } else { span_data.ctxt },
)
}