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Revised span-to-lines conversion to produce an empty vec on DUMMY_SP.
This required revising some of the client code to stop relying on
the returned set of lines being non-empty.
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pnkfelix committed Mar 20, 2020
1 parent f4c675c commit ebf27fa
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Showing 3 changed files with 11 additions and 4 deletions.
2 changes: 1 addition & 1 deletion src/librustc_errors/emitter.rs
Expand Up @@ -1574,7 +1574,7 @@ impl EmitterWriter {
.span_to_lines(parts[0].span)
.expect("span_to_lines failed when emitting suggestion");

assert!(!lines.lines.is_empty());
assert!(!lines.lines.is_empty() || parts[0].span.is_dummy());

let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
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6 changes: 3 additions & 3 deletions src/librustc_errors/lib.rs
Expand Up @@ -194,7 +194,7 @@ impl CodeSuggestion {
let bounding_span = Span::with_root_ctxt(lo, hi);
// The different spans might belong to different contexts, if so ignore suggestion.
let lines = sm.span_to_lines(bounding_span).ok()?;
assert!(!lines.lines.is_empty());
assert!(!lines.lines.is_empty() || bounding_span.is_dummy());

// We can't splice anything if the source is unavailable.
if !sm.ensure_source_file_source_present(lines.file.clone()) {
Expand All @@ -213,8 +213,8 @@ impl CodeSuggestion {
let sf = &lines.file;
let mut prev_hi = sm.lookup_char_pos(bounding_span.lo());
prev_hi.col = CharPos::from_usize(0);

let mut prev_line = sf.get_line(lines.lines[0].line_index);
let mut prev_line =
lines.lines.get(0).and_then(|line0| sf.get_line(line0.line_index));
let mut buf = String::new();

for part in &substitution.parts {
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7 changes: 7 additions & 0 deletions src/librustc_span/source_map.rs
Expand Up @@ -535,6 +535,10 @@ impl SourceMap {
let (lo, hi) = self.is_valid_span(sp)?;
assert!(hi.line >= lo.line);

if sp.is_dummy() {
return Ok(FileLines { file: lo.file, lines: Vec::new() });
}

let mut lines = Vec::with_capacity(hi.line - lo.line + 1);

// The span starts partway through the first line,
Expand All @@ -545,6 +549,9 @@ impl SourceMap {
// and to the end of the line. Be careful because the line
// numbers in Loc are 1-based, so we subtract 1 to get 0-based
// lines.
//
// FIXME: now that we handle DUMMY_SP up above, we should consider
// aseerting the line numbers here are all indeed 1-based.
let hi_line = hi.line.saturating_sub(1);
for line_index in lo.line.saturating_sub(1)..hi_line {
let line_len = lo.file.get_line(line_index).map(|s| s.chars().count()).unwrap_or(0);
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