better help text for "match -> if let" lint
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.
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15
src/misc.rs
15
src/misc.rs
@ -43,13 +43,20 @@ impl LintPass for MiscPass {
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// an enum is extended. So we only consider cases where a `_` wildcard is used
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if arms[1].pats[0].node == PatWild(PatWildSingle) &&
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arms[0].pats.len() == 1 {
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let body_code = snippet(cx, arms[0].body.span, "..");
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let suggestion = if let ExprBlock(_) = arms[0].body.node {
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body_code.into_owned()
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} else {
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format!("{{ {} }}", body_code)
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};
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span_help_and_lint(cx, SINGLE_MATCH, expr.span,
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"You seem to be trying to use match for \
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destructuring a single type. Did you mean to \
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destructuring a single pattern. Did you mean to \
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use `if let`?",
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&*format!("Try if let {} = {} {{ ... }}",
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snippet(cx, arms[0].pats[0].span, ".."),
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snippet(cx, ex.span, ".."))
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&*format!("Try\nif let {} = {} {}",
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snippet(cx, arms[0].pats[0].span, ".."),
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snippet(cx, ex.span, ".."),
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suggestion)
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);
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}
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}
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@ -77,10 +77,10 @@ pub fn span_lint(cx: &Context, lint: &'static Lint, sp: Span, msg: &str) {
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cx.span_lint(lint, sp, msg);
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}
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pub fn span_help_and_lint(cx: &Context, lint: &'static Lint, span: Span,
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pub fn span_help_and_lint(cx: &Context, lint: &'static Lint, span: Span,
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msg: &str, help: &str) {
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span_lint(cx, lint, span, msg);
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if cx.current_level(lint) != Level::Allow {
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cx.sess().span_help(span, help);
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cx.sess().fileline_help(span, help);
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}
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}
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8
tests/compile-fail/match_if_let.rs
Normal file → Executable file
8
tests/compile-fail/match_if_let.rs
Normal file → Executable file
@ -6,8 +6,10 @@
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fn main(){
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let x = Some(1u8);
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match x { //~ ERROR You seem to be trying to use match
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//~^ HELP Try if let Some(y) = x { ... }
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Some(y) => println!("{:?}", y),
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//~^ HELP Try
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Some(y) => {
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println!("{:?}", y);
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}
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_ => ()
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}
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// Not linted
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@ -17,7 +19,7 @@ fn main(){
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}
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let z = (1u8,1u8);
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match z { //~ ERROR You seem to be trying to use match
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//~^ HELP Try if let (2...3, 7...9) = z { ... }
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//~^ HELP Try
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(2...3, 7...9) => println!("{:?}", z),
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_ => {}
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}
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