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matches: special message for this case

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match &e { &Pat1 => {}, &Pat2 => {}, ... }

(inspired by dogfood fixes)
This commit is contained in:
Georg Brandl 2015-08-21 20:49:59 +02:00
parent 8f1a237493
commit 7580da306e
2 changed files with 20 additions and 13 deletions
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27
src/matches.rs
View File

@ -55,9 +55,15 @@ impl LintPass for MatchPass {
// check preconditions for MATCH_REF_PATS
if has_only_ref_pats(arms) {
span_lint(cx, MATCH_REF_PATS, expr.span, &format!(
"instead of prefixing all patterns with `&`, you can dereference the \
expression to match: `match *{} {{ ...`", snippet(cx, ex.span, "..")));
if let ExprAddrOf(Mutability::MutImmutable, ref inner) = ex.node {
span_lint(cx, MATCH_REF_PATS, expr.span, &format!(
"you don't need to add `&` to both the expression to match \
and the patterns: use `match {} {{ ...`", snippet(cx, inner.span, "..")));
} else {
span_lint(cx, MATCH_REF_PATS, expr.span, &format!(
"instead of prefixing all patterns with `&`, you can dereference the \
expression to match: `match *{} {{ ...`", snippet(cx, ex.span, "..")));
}
}
}
}
@ -72,14 +78,9 @@ fn is_unit_expr(expr: &Expr) -> bool {
}
fn has_only_ref_pats(arms: &[Arm]) -> bool {
for arm in arms {
for pat in &arm.pats {
match pat.node {
PatRegion(..) => (), // &-patterns
PatWild(..) => (), // an "anything" wildcard is also fine
_ => return false,
}
}
}
true
arms.iter().flat_map(|a| &a.pats).all(|p| match p.node {
PatRegion(..) => true, // &-patterns
PatWild(..) => true, // an "anything" wildcard is also fine
_ => false,
})
}

6
tests/compile-fail/matches.rs
View File

@ -53,6 +53,12 @@ fn ref_pats() {
&(v, 1) => println!("{}", v),
_ => println!("none"),
}
// special case: using & both in expr and pats
let w = Some(0);
match &w { //~ERROR you don't need to add `&` to both
&Some(v) => println!("{:?}", v),
&None => println!("none"),
}
}
fn main() {