mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-19 09:33:36 +00:00
47 lines
2 KiB
Rust
47 lines
2 KiB
Rust
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use syntax::ptr::P;
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use syntax::ast;
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use syntax::ast::*;
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use rustc::lint::{Context, LintPass, LintArray, Lint, Level};
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use syntax::codemap::Span;
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use types::span_note_and_lint;
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/// Handles uncategorized lints
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/// Currently handles linting of if-let-able matches
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pub struct MiscPass;
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declare_lint!(CLIPPY_SINGLE_MATCH, Warn,
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"Warn on usage of matches with a single nontrivial arm")
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impl LintPass for MiscPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(CLIPPY_SINGLE_MATCH)
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}
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fn check_expr(&mut self, cx: &Context, expr: &Expr) {
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if let ExprMatch(ref ex, ref arms, MatchNormal) = expr.node {
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if arms.len() == 2 {
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if arms[0].guard.is_none() && arms[1].pats.len() == 1 {
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match arms[1].body.node {
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ExprTup(ref v) if v.len() == 0 && arms[1].guard.is_none() => (),
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ExprBlock(ref b) if b.stmts.len() == 0 && arms[1].guard.is_none() => (),
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_ => return
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}
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// In some cases, an exhaustive match is preferred to catch situations when
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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) && arms[0].pats.len() == 1 {
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let map = cx.sess().codemap();
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span_note_and_lint(cx, CLIPPY_SINGLE_MATCH, expr.span,
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"You seem to be trying to use match for destructuring a single type. Did you mean to use `if let`?",
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format!("Try if let {} = {} {{ ... }}",
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map.span_to_snippet(arms[0].pats[0].span).unwrap_or("..".to_string()),
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map.span_to_snippet(ex.span).unwrap_or("..".to_string())).as_slice()
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);
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}
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}
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}
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}
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}
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}
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