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Rollup merge of rust-lang#68256 - estebank:bad-sugg-span, r=petrochenkov
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Do not ICE on malformed suggestion spans

Under the assumption that suggestions are by their very nature always "best effort", it is ok if we don't display them instead of having an ICE. The underlying issue of the malformed span being _created_ is left unaddressed.

Fix rust-lang#67567.

r? @petrochenkov
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tmandry authored Jan 18, 2020
2 parents fca3264 + 03240e1 commit 7f6fdef
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Showing 4 changed files with 30 additions and 9 deletions.
16 changes: 12 additions & 4 deletions src/librustc_errors/emitter.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1476,6 +1476,15 @@ impl EmitterWriter {
None => return Ok(()),
};

// Render the replacements for each suggestion
let suggestions = suggestion.splice_lines(&**sm);

if suggestions.is_empty() {
// Suggestions coming from macros can have malformed spans. This is a heavy handed
// approach to avoid ICEs by ignoring the suggestion outright.
return Ok(());
}

let mut buffer = StyledBuffer::new();

// Render the suggestion message
Expand All @@ -1492,9 +1501,6 @@ impl EmitterWriter {
Some(Style::HeaderMsg),
);

// Render the replacements for each suggestion
let suggestions = suggestion.splice_lines(&**sm);

let mut row_num = 2;
let mut notice_capitalization = false;
for (complete, parts, only_capitalization) in suggestions.iter().take(MAX_SUGGESTIONS) {
Expand All @@ -1505,7 +1511,9 @@ impl EmitterWriter {
let show_underline = !(parts.len() == 1 && parts[0].snippet.trim() == complete.trim())
&& complete.lines().count() == 1;

let lines = sm.span_to_lines(parts[0].span).unwrap();
let lines = sm
.span_to_lines(parts[0].span)
.expect("span_to_lines failed when emitting suggestion");

assert!(!lines.lines.is_empty());

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10 changes: 10 additions & 0 deletions src/librustc_errors/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@

pub use emitter::ColorConfig;

use log::debug;
use Level::*;

use emitter::{is_case_difference, Emitter, EmitterWriter};
Expand Down Expand Up @@ -174,6 +175,15 @@ impl CodeSuggestion {

self.substitutions
.iter()
.filter(|subst| {
// Suggestions coming from macros can have malformed spans. This is a heavy
// handed approach to avoid ICEs by ignoring the suggestion outright.
let invalid = subst.parts.iter().any(|item| cm.is_valid_span(item.span).is_err());
if invalid {
debug!("splice_lines: suggestion contains an invalid span: {:?}", subst);
}
!invalid
})
.cloned()
.map(|mut substitution| {
// Assumption: all spans are in the same file, and all spans
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11 changes: 7 additions & 4 deletions src/librustc_span/source_map.rs
Original file line number Diff line number Diff line change
Expand Up @@ -473,20 +473,23 @@ impl SourceMap {
lo.line != hi.line
}

pub fn span_to_lines(&self, sp: Span) -> FileLinesResult {
debug!("span_to_lines(sp={:?})", sp);

pub fn is_valid_span(&self, sp: Span) -> Result<(Loc, Loc), SpanLinesError> {
let lo = self.lookup_char_pos(sp.lo());
debug!("span_to_lines: lo={:?}", lo);
let hi = self.lookup_char_pos(sp.hi());
debug!("span_to_lines: hi={:?}", hi);

if lo.file.start_pos != hi.file.start_pos {
return Err(SpanLinesError::DistinctSources(DistinctSources {
begin: (lo.file.name.clone(), lo.file.start_pos),
end: (hi.file.name.clone(), hi.file.start_pos),
}));
}
Ok((lo, hi))
}

pub fn span_to_lines(&self, sp: Span) -> FileLinesResult {
debug!("span_to_lines(sp={:?})", sp);
let (lo, hi) = self.is_valid_span(sp)?;
assert!(hi.line >= lo.line);

let mut lines = Vec::with_capacity(hi.line - lo.line + 1);
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2 changes: 1 addition & 1 deletion src/test/ui/consts/miri_unleashed/mutable_const2.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ error: internal compiler error: mutable allocation in constant
LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:346:17
thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:356:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic
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