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Improve the MATCH_REF_PATS suggestions

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This commit is contained in:
mcarton 2016-03-09 16:22:31 +01:00
parent 3ab4914a29
commit 9cfc6124a3
2 changed files with 42 additions and 19 deletions
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36
src/matches.rs
View file

@ -8,7 +8,7 @@ use std::cmp::Ordering;
use syntax::ast::LitKind;
use syntax::codemap::Span;
use utils::{COW_PATH, OPTION_PATH, RESULT_PATH};
use utils::{match_type, snippet, span_lint, span_note_and_lint, span_lint_and_then, in_external_macro, expr_block};
use utils::{match_type, snippet, span_note_and_lint, span_lint_and_then, in_external_macro, expr_block};
/// **What it does:** This lint checks for matches with a single arm where an `if let` will usually suffice.
///
@ -309,18 +309,26 @@ fn check_match_ref_pats(cx: &LateContext, ex: &Expr, arms: &[Arm], source: Match
if has_only_ref_pats(arms) {
if let ExprAddrOf(Mutability::MutImmutable, ref inner) = ex.node {
let template = match_template(cx, expr.span, source, "", inner);
span_lint(cx,
MATCH_REF_PATS,
expr.span,
&format!("you don't need to add `&` to both the expression and the patterns: use `{}`",
template));
span_lint_and_then(cx,
MATCH_REF_PATS,
expr.span,
"you don't need to add `&` to both the expression and the patterns",
|db| {
db.span_suggestion(expr.span,
"try",
template);
});
} else {
let template = match_template(cx, expr.span, source, "*", ex);
span_lint(cx,
MATCH_REF_PATS,
expr.span,
&format!("instead of prefixing all patterns with `&`, you can dereference the expression: `{}`",
template));
span_lint_and_then(cx,
MATCH_REF_PATS,
expr.span,
"you don't need to add `&` to all patterns",
|db| {
db.span_suggestion(expr.span,
"instead of prefixing all patterns with `&`, you can dereference the expression",
template);
});
}
}
}
@ -435,9 +443,9 @@ fn has_only_ref_pats(arms: &[Arm]) -> bool {
fn match_template(cx: &LateContext, span: Span, source: MatchSource, op: &str, expr: &Expr) -> String {
let expr_snippet = snippet(cx, expr.span, "..");
match source {
MatchSource::Normal => format!("match {}{} {{ ...", op, expr_snippet),
MatchSource::IfLetDesugar { .. } => format!("if let ... = {}{} {{", op, expr_snippet),
MatchSource::WhileLetDesugar => format!("while let ... = {}{} {{", op, expr_snippet),
MatchSource::Normal => format!("match {}{} {{ .. }}", op, expr_snippet),
MatchSource::IfLetDesugar { .. } => format!("if let .. = {}{} {{ .. }}", op, expr_snippet),
MatchSource::WhileLetDesugar => format!("while let .. = {}{} {{ .. }}", op, expr_snippet),
MatchSource::ForLoopDesugar => cx.sess().span_bug(span, "for loop desugared to match with &-patterns!"),
MatchSource::TryDesugar => cx.sess().span_bug(span, "`?` operator desugared to match with &-patterns!")
}

25
tests/compile-fail/matches.rs
View file

@ -137,7 +137,10 @@ fn match_bool() {
fn ref_pats() {
{
let v = &Some(0);
match v { //~ERROR dereference the expression: `match *v { ...`
match v {
//~^ERROR add `&` to all patterns
//~|HELP instead of
//~|SUGGESTION `match *v { .. }`
&Some(v) => println!("{:?}", v),
&None => println!("none"),
}
@ -147,13 +150,19 @@ fn ref_pats() {
}
}
let tup =& (1, 2);
match tup { //~ERROR dereference the expression: `match *tup { ...`
match tup {
//~^ERROR add `&` to all patterns
//~|HELP instead of
//~|SUGGESTION `match *tup { .. }`
&(v, 1) => println!("{}", v),
_ => println!("none"),
}
// special case: using & both in expr and pats
let w = Some(0);
match &w { //~ERROR use `match w { ...`
match &w {
//~^ERROR add `&` to both
//~|HELP try
//~|SUGGESTION `match w { .. }`
&Some(v) => println!("{:?}", v),
&None => println!("none"),
}
@ -164,12 +173,18 @@ fn ref_pats() {
}
let a = &Some(0);
if let &None = a { //~ERROR dereference the expression: `if let ... = *a {`
if let &None = a {
//~^ERROR add `&` to all patterns
//~|HELP instead of
//~|SUGGESTION `if let ... = *a { .. }`
println!("none");
}
let b = Some(0);
if let &None = &b { //~ERROR use `if let ... = b {`
if let &None = &b {
//~^ERROR add `&` to both
//~|HELP try
//~|SUGGESTION `if let ... = b { .. }`
println!("none");
}
}