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better help text for "match -> if let" lint

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Implements the suggestion from #87.

Changes span_help_and_lint(), which is only used for this lint,
to use fileline_help() instead of span_help() to avoid printing
the span twice.

Also adds complete suggested new code. I had to distinguish
between blocks, which need no additionals braces, and other exprs.
This commit is contained in:
Georg Brandl 2015-08-11 19:26:33 +02:00
parent 50ebdaa79d
commit cab9905705
3 changed files with 18 additions and 9 deletions
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15
src/misc.rs
View file

@ -43,13 +43,20 @@ impl LintPass for MiscPass {
// an enum is extended. So we only consider cases where a `_` wildcard is used
if arms[1].pats[0].node == PatWild(PatWildSingle) &&
arms[0].pats.len() == 1 {
let body_code = snippet(cx, arms[0].body.span, "..");
let suggestion = if let ExprBlock(_) = arms[0].body.node {
body_code.into_owned()
} else {
format!("{{ {} }}", body_code)
};
span_help_and_lint(cx, SINGLE_MATCH, expr.span,
"You seem to be trying to use match for \
destructuring a single type. Did you mean to \
destructuring a single pattern. Did you mean to \
use `if let`?",
&*format!("Try if let {} = {} {{ ... }}",
snippet(cx, arms[0].pats[0].span, ".."),
snippet(cx, ex.span, ".."))
&*format!("Try\nif let {} = {} {}",
snippet(cx, arms[0].pats[0].span, ".."),
snippet(cx, ex.span, ".."),
suggestion)
);
}
}