73 lines
3.0 KiB
Rust
73 lines
3.0 KiB
Rust
use crate::utils::{is_type_diagnostic_item, method_chain_args, snippet_with_applicability, span_lint_and_sugg};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, MatchSource, PatKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:*** Checks for unnecessary `ok()` in if let.
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///
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/// **Why is this bad?** Calling `ok()` in if let is unnecessary, instead match
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/// on `Ok(pat)`
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```ignore
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/// for i in iter {
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/// if let Some(value) = i.parse().ok() {
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/// vec.push(value)
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/// }
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/// }
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/// ```
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/// Could be written:
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///
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/// ```ignore
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/// for i in iter {
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/// if let Ok(value) = i.parse() {
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/// vec.push(value)
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/// }
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/// }
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/// ```
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pub IF_LET_SOME_RESULT,
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style,
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"usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead"
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}
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declare_lint_pass!(OkIfLet => [IF_LET_SOME_RESULT]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for OkIfLet {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! { //begin checking variables
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if let ExprKind::Match(ref op, ref body, source) = expr.kind; //test if expr is a match
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if let MatchSource::IfLetDesugar { .. } = source; //test if it is an If Let
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if let ExprKind::MethodCall(_, ok_span, ref result_types) = op.kind; //check is expr.ok() has type Result<T,E>.ok()
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if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pat.kind; //get operation
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if method_chain_args(op, &["ok"]).is_some(); //test to see if using ok() methoduse std::marker::Sized;
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if is_type_diagnostic_item(cx, cx.tables.expr_ty(&result_types[0]), sym!(result_type));
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if rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_path(x, false)) == "Some";
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then {
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let mut applicability = Applicability::MachineApplicable;
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let some_expr_string = snippet_with_applicability(cx, y[0].span, "", &mut applicability);
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let trimmed_ok = snippet_with_applicability(cx, op.span.until(ok_span), "", &mut applicability);
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let sugg = format!(
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"if let Ok({}) = {}",
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some_expr_string,
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trimmed_ok.trim().trim_end_matches('.'),
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);
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span_lint_and_sugg(
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cx,
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IF_LET_SOME_RESULT,
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expr.span.with_hi(op.span.hi()),
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"Matching on `Some` with `ok()` is redundant",
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&format!("Consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string),
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sugg,
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applicability,
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);
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}
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}
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}
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}
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