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incr.comp.: Make Span decoding more consistent so it doesn't mess up -Zincremental-verify-ich

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This commit is contained in:
Michael Woerister 2017-12-07 12:31:40 +01:00
parent 1c0e611dff
commit f5bd1ca678
1 changed files with 21 additions and 13 deletions
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34
src/librustc_metadata/decoder.rs
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@ -273,25 +273,23 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for DecodeContext<'a, 'tcx> {
let lo = BytePos::decode(self)?;
let hi = BytePos::decode(self)?;
if lo == BytePos(0) && hi == BytePos(0) {
// Don't try to rebase DUMMY_SP. Otherwise it will look like a valid
// Span again.
return Ok(DUMMY_SP)
}
if hi < lo {
// Consistently map invalid spans to DUMMY_SP.
return Ok(DUMMY_SP)
}
let sess = if let Some(sess) = self.sess {
sess
} else {
bug!("Cannot decode Span without Session.")
};
let (lo, hi) = if lo > hi {
// Currently macro expansion sometimes produces invalid Span values
// where lo > hi. In order not to crash the compiler when trying to
// translate these values, let's transform them into something we
// can handle (and which will produce useful debug locations at
// least some of the time).
// This workaround is only necessary as long as macro expansion is
// not fixed. FIXME(#23480)
(lo, lo)
} else {
(lo, hi)
};
let imported_filemaps = self.cdata().imported_filemaps(&sess.codemap());
let filemap = {
// Optimize for the case that most spans within a translated item
@ -321,6 +319,16 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for DecodeContext<'a, 'tcx> {
}
};
// Make sure our binary search above is correct.
debug_assert!(lo >= filemap.original_start_pos &&
lo <= filemap.original_end_pos);
if hi < filemap.original_start_pos || hi > filemap.original_end_pos {
// `hi` points to a different FileMap than `lo` which is invalid.
// Again, map invalid Spans to DUMMY_SP.
return Ok(DUMMY_SP)
}
let lo = (lo + filemap.translated_filemap.start_pos) - filemap.original_start_pos;
let hi = (hi + filemap.translated_filemap.start_pos) - filemap.original_start_pos;