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Rollup merge of #91607 - FabianWolff:issue-91560-const-span, r=jackh726

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Make `span_extend_to_prev_str()` more robust

Fixes #91560. The logic in `span_extend_to_prev_str()` is currently quite brittle and fails if there is extra whitespace or something else in between, and it also should return an `Option` but doesn't currently.
This commit is contained in:
Matthias Krüger 2022-02-11 21:48:43 +01:00 • committed by GitHub
commit b7c48b4691
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7 changed files with 123 additions and 46 deletions
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40
compiler/rustc_span/src/source_map.rs
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@ -629,26 +629,41 @@ impl SourceMap {
}
/// Extends the given `Span` to just after the previous occurrence of `pat` when surrounded by
/// whitespace. Returns the same span if no character could be found or if an error occurred
/// while retrieving the code snippet.
pub fn span_extend_to_prev_str(&self, sp: Span, pat: &str, accept_newlines: bool) -> Span {
/// whitespace. Returns None if the pattern could not be found or if an error occurred while
/// retrieving the code snippet.
pub fn span_extend_to_prev_str(
&self,
sp: Span,
pat: &str,
accept_newlines: bool,
include_whitespace: bool,
) -> Option<Span> {
// assure that the pattern is delimited, to avoid the following
// fn my_fn()
// ^^^^ returned span without the check
// ---------- correct span
let prev_source = self.span_to_prev_source(sp).ok()?;
for ws in &[" ", "\t", "\n"] {
let pat = pat.to_owned() + ws;
if let Ok(prev_source) = self.span_to_prev_source(sp) {
let prev_source = prev_source.rsplit(&pat).next().unwrap_or("").trim_start();
if prev_source.is_empty() && sp.lo().0 != 0 {
return sp.with_lo(BytePos(sp.lo().0 - 1));
} else if accept_newlines || !prev_source.contains('\n') {
return sp.with_lo(BytePos(sp.lo().0 - prev_source.len() as u32));
if let Some(pat_pos) = prev_source.rfind(&pat) {
let just_after_pat_pos = pat_pos + pat.len() - 1;
let just_after_pat_plus_ws = if include_whitespace {
just_after_pat_pos
+ prev_source[just_after_pat_pos..]
.find(|c: char| !c.is_whitespace())
.unwrap_or(0)
} else {
just_after_pat_pos
};
let len = prev_source.len() - just_after_pat_plus_ws;
let prev_source = &prev_source[just_after_pat_plus_ws..];
if accept_newlines || !prev_source.trim_start().contains('\n') {
return Some(sp.with_lo(BytePos(sp.lo().0 - len as u32)));
}
}
}
sp
None
}
/// Returns the source snippet as `String` after the given `Span`.
@ -927,7 +942,7 @@ impl SourceMap {
}
pub fn generate_fn_name_span(&self, span: Span) -> Option<Span> {
let prev_span = self.span_extend_to_prev_str(span, "fn", true);
let prev_span = self.span_extend_to_prev_str(span, "fn", true, true).unwrap_or(span);
if let Ok(snippet) = self.span_to_snippet(prev_span) {
debug!(
"generate_fn_name_span: span={:?}, prev_span={:?}, snippet={:?}",
@ -968,8 +983,7 @@ impl SourceMap {
pub fn generate_local_type_param_snippet(&self, span: Span) -> Option<(Span, String)> {
// Try to extend the span to the previous "fn" keyword to retrieve the function
// signature.
let sugg_span = self.span_extend_to_prev_str(span, "fn", false);
if sugg_span != span {
if let Some(sugg_span) = self.span_extend_to_prev_str(span, "fn", false, true) {
if let Ok(snippet) = self.span_to_snippet(sugg_span) {
// Consume the function name.
let mut offset = snippet