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tweak "make mut" spans when assigning to locals

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Ezra Shaw 2023-04-19 18:22:03 +12:00 • committed by Ezra Shaw
parent 3320f2fab6
commit fd8aa5ec7d
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12 changed files with 46 additions and 41 deletions
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56
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
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@ -1202,36 +1202,42 @@ fn suggest_ampmut<'tcx>(
opt_assignment_rhs_span: Option<Span>,
opt_ty_info: Option<Span>,
) -> (bool, Span, String) {
// if there is a RHS and it starts with a `&` from it, then check if it is
// mutable, and if not, put suggest putting `mut ` to make it mutable.
// we don't have to worry about lifetime annotations here because they are
// not valid when taking a reference. For example, the following is not valid Rust:
//
// let x: &i32 = &'a 5;
// ^^ lifetime annotation not allowed
//
if let Some(assignment_rhs_span) = opt_assignment_rhs_span
&& let Ok(src) = tcx.sess.source_map().span_to_snippet(assignment_rhs_span)
&& let Some(stripped) = src.strip_prefix('&')
{
let is_mutbl = |ty: &str| -> bool {
if let Some(rest) = ty.strip_prefix("mut") {
match rest.chars().next() {
// e.g. `&mut x`
Some(c) if c.is_whitespace() => true,
// e.g. `&mut(x)`
Some('(') => true,
// e.g. `&mut{x}`
Some('{') => true,
// e.g. `&mutablevar`
_ => false,
}
} else {
false
let is_mut = if let Some(rest) = stripped.trim_start().strip_prefix("mut") {
match rest.chars().next() {
// e.g. `&mut x`
Some(c) if c.is_whitespace() => true,
// e.g. `&mut(x)`
Some('(') => true,
// e.g. `&mut{x}`
Some('{') => true,
// e.g. `&mutablevar`
_ => false,
}
} else {
false
};
if let (true, Some(ws_pos)) = (src.starts_with("&'"), src.find(char::is_whitespace)) {
let lt_name = &src[1..ws_pos];
let ty = src[ws_pos..].trim_start();
if !is_mutbl(ty) {
return (true, assignment_rhs_span, format!("&{lt_name} mut {ty}"));
}
} else if let Some(stripped) = src.strip_prefix('&') {
let stripped = stripped.trim_start();
if !is_mutbl(stripped) {
return (true, assignment_rhs_span, format!("&mut {stripped}"));
}
// if the reference is already mutable then there is nothing we can do
// here.
if !is_mut {
let span = assignment_rhs_span;
// shrink the span to just after the `&` in `&variable`
let span = span.with_lo(span.lo() + BytePos(1)).shrink_to_lo();
// FIXME(Ezrashaw): returning is bad because we still might want to
// update the annotated type, see #106857.
return (true, span, "mut ".to_owned());
}
}