97 lines
3.3 KiB
Rust
97 lines
3.3 KiB
Rust
use rustc::lint::*;
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use rustc::hir::*;
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use syntax::ast::NodeId;
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use utils::{in_macro, match_def_path, match_trait_method, same_tys, snippet, span_lint_and_then};
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use utils::{opt_def_id, paths, resolve_node};
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/// **What it does:** Checks for always-identical `Into`/`From` conversions.
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///
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/// **Why is this bad?** Redundant code.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// // format!() returns a `String`
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/// let s: String = format!("hello").into();
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/// ```
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declare_lint! {
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pub IDENTITY_CONVERSION,
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Warn,
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"using always-identical `Into`/`From` conversions"
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}
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#[derive(Default)]
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pub struct IdentityConversion {
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try_desugar_arm: Vec<NodeId>,
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}
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impl LintPass for IdentityConversion {
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fn get_lints(&self) -> LintArray {
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lint_array!(IDENTITY_CONVERSION)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityConversion {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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if in_macro(e.span) {
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return;
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}
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if Some(&e.id) == self.try_desugar_arm.last() {
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return;
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}
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match e.node {
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ExprMatch(_, ref arms, MatchSource::TryDesugar) => {
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let e = match arms[0].body.node {
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ExprRet(Some(ref e)) | ExprBreak(_, Some(ref e)) => e,
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_ => return,
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};
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if let ExprCall(_, ref args) = e.node {
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self.try_desugar_arm.push(args[0].id);
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} else {
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return;
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}
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},
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ExprMethodCall(ref name, .., ref args) => {
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if match_trait_method(cx, e, &paths::INTO[..]) && &*name.name.as_str() == "into" {
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let a = cx.tables.expr_ty(e);
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let b = cx.tables.expr_ty(&args[0]);
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if same_tys(cx, a, b) {
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let sugg = snippet(cx, args[0].span, "<expr>").into_owned();
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span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
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db.span_suggestion(e.span, "consider removing `.into()`", sugg);
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});
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}
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}
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},
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ExprCall(ref path, ref args) => if let ExprPath(ref qpath) = path.node {
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if let Some(def_id) = opt_def_id(resolve_node(cx, qpath, path.hir_id)) {
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if match_def_path(cx.tcx, def_id, &paths::FROM_FROM[..]) {
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let a = cx.tables.expr_ty(e);
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let b = cx.tables.expr_ty(&args[0]);
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if same_tys(cx, a, b) {
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let sugg = snippet(cx, args[0].span, "<expr>").into_owned();
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let sugg_msg = format!("consider removing `{}()`", snippet(cx, path.span, "From::from"));
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span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
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db.span_suggestion(e.span, &sugg_msg, sugg);
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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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}
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fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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if Some(&e.id) == self.try_desugar_arm.last() {
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self.try_desugar_arm.pop();
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}
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}
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}
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