86 lines
2.7 KiB
Rust
86 lines
2.7 KiB
Rust
use rustc::lint::*;
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use rustc::hir::*;
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use utils::{match_qpath, paths, snippet, span_lint_and_then};
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/// **What it does:*** Lint for redundant pattern matching over `Result` or
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/// `Option`
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///
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/// **Why is this bad?** It's more concise and clear to just use the proper
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/// utility function
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// if let Ok(_) = Ok::<i32, i32>(42) {}
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/// if let Err(_) = Err::<i32, i32>(42) {}
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/// if let None = None::<()> {}
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/// if let Some(_) = Some(42) {}
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/// ```
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///
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/// The more idiomatic use would be:
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///
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/// ```rust
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/// if Ok::<i32, i32>(42).is_ok() {}
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/// if Err::<i32, i32>(42).is_err() {}
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/// if None::<()>.is_none() {}
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/// if Some(42).is_some() {}
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/// ```
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///
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declare_lint! {
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pub IF_LET_REDUNDANT_PATTERN_MATCHING,
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Warn,
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"use the proper utility function avoiding an `if let`"
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}
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#[derive(Copy, Clone)]
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pub struct Pass;
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(IF_LET_REDUNDANT_PATTERN_MATCHING)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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if let ExprMatch(ref op, ref arms, MatchSource::IfLetDesugar { .. }) = expr.node {
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if arms[0].pats.len() == 1 {
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let good_method = match arms[0].pats[0].node {
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PatKind::TupleStruct(ref path, ref pats, _) if pats.len() == 1 && pats[0].node == PatKind::Wild => {
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if match_qpath(path, &paths::RESULT_OK) {
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"is_ok()"
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} else if match_qpath(path, &paths::RESULT_ERR) {
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"is_err()"
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} else if match_qpath(path, &paths::OPTION_SOME) {
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"is_some()"
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} else {
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return;
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}
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},
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PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => "is_none()",
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_ => return,
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};
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span_lint_and_then(
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cx,
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IF_LET_REDUNDANT_PATTERN_MATCHING,
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arms[0].pats[0].span,
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&format!("redundant pattern matching, consider using `{}`", good_method),
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|db| {
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let span = expr.span.with_hi(op.span.hi());
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db.span_suggestion(
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span,
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"try this",
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format!("if {}.{}", snippet(cx, op.span, "_"), good_method),
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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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