2019-02-10 05:58:51 -06:00
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use if_chain::if_chain;
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2018-12-29 09:04:45 -06:00
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use rustc::hir::*;
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2019-02-25 06:40:28 -06:00
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use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
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2018-12-29 09:04:45 -06:00
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use rustc::ty;
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use rustc::{declare_tool_lint, lint_array};
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use rustc_errors::Applicability;
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2015-07-26 09:53:11 -05:00
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2019-01-30 19:15:29 -06:00
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use crate::utils::{is_adjusted, iter_input_pats, snippet_opt, span_lint_and_then, type_is_unsafe_function};
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2015-05-10 00:09:04 -05:00
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pub struct EtaPass;
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2019-03-05 10:50:33 -06:00
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/// **What it does:** Checks for closures which just call another function where
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/// the function can be called directly. `unsafe` functions or calls where types
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/// get adjusted are ignored.
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///
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/// **Why is this bad?** Needlessly creating a closure adds code for no benefit
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/// and gives the optimizer more work.
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///
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/// **Known problems:** If creating the closure inside the closure has a side-
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/// effect then moving the closure creation out will change when that side-
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/// effect runs.
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2019-01-30 19:15:29 -06:00
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/// See rust-lang/rust-clippy#1439 for more details.
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2019-03-05 10:50:33 -06:00
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///
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/// **Example:**
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/// ```rust,ignore
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2019-03-05 10:50:33 -06:00
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/// xs.map(|x| foo(x))
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/// ```
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/// where `foo(_)` is a plain function that takes the exact argument type of
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/// `x`.
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2016-08-06 03:18:36 -05:00
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pub REDUNDANT_CLOSURE,
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2018-03-28 08:24:26 -05:00
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style,
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"redundant closures, i.e., `|a| foo(a)` (which can be written as just `foo`)"
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2016-02-05 17:13:29 -06:00
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}
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2015-05-10 00:09:04 -05:00
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impl LintPass for EtaPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(REDUNDANT_CLOSURE)
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}
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2019-01-26 13:40:55 -06:00
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fn name(&self) -> &'static str {
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"EtaReduction"
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}
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2015-09-18 21:53:04 -05:00
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}
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2015-05-10 00:09:04 -05:00
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2016-12-07 06:13:40 -06:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EtaPass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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2019-02-25 06:40:28 -06:00
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if in_external_macro(cx.sess(), expr.span) {
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return;
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}
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2015-08-21 13:44:48 -05:00
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match expr.node {
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ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
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for arg in args {
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check_closure(cx, arg)
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}
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2016-12-20 11:21:30 -06:00
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},
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2015-08-14 07:21:05 -05:00
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_ => (),
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}
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}
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}
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2018-07-23 06:01:12 -05:00
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fn check_closure(cx: &LateContext<'_, '_>, expr: &Expr) {
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2018-07-12 02:30:57 -05:00
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if let ExprKind::Closure(_, ref decl, eid, _, _) = expr.node {
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2018-12-07 18:56:03 -06:00
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let body = cx.tcx.hir().body(eid);
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2017-01-04 17:48:34 -06:00
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let ex = &body.value;
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if_chain!(
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if let ExprKind::Call(ref caller, ref args) = ex.node;
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// Not the same number of arguments, there is no way the closure is the same as the function return;
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if args.len() == decl.inputs.len();
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// Are the expression or the arguments type-adjusted? Then we need the closure
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if !(is_adjusted(cx, ex) || args.iter().any(|arg| is_adjusted(cx, arg)));
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2017-01-13 10:04:56 -06:00
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let fn_ty = cx.tables.expr_ty(caller);
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if !type_is_unsafe_function(cx, fn_ty);
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if compare_inputs(&mut iter_input_pats(decl, body), &mut args.into_iter());
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then {
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span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |db| {
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if let Some(snippet) = snippet_opt(cx, caller.span) {
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db.span_suggestion(
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expr.span,
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"remove closure as shown",
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snippet,
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Applicability::MachineApplicable,
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);
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2016-11-16 14:57:56 -06:00
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}
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});
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2016-11-16 14:57:56 -06:00
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}
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);
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if_chain!(
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if let ExprKind::MethodCall(ref path, _, ref args) = ex.node;
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// Not the same number of arguments, there is no way the closure is the same as the function return;
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if args.len() == decl.inputs.len();
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// Are the expression or the arguments type-adjusted? Then we need the closure
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if !(is_adjusted(cx, ex) || args.iter().skip(1).any(|arg| is_adjusted(cx, arg)));
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let method_def_id = cx.tables.type_dependent_defs()[ex.hir_id].def_id();
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if !type_is_unsafe_function(cx, cx.tcx.type_of(method_def_id));
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if compare_inputs(&mut iter_input_pats(decl, body), &mut args.into_iter());
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if let Some(name) = get_ufcs_type_name(cx, method_def_id, &args[0]);
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then {
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span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |db| {
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2019-01-27 06:33:56 -06:00
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db.span_suggestion(
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2018-09-18 10:07:54 -05:00
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expr.span,
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"remove closure as shown",
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2019-02-10 05:58:51 -06:00
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format!("{}::{}", name, path.ident.name),
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2018-09-18 12:01:17 -05:00
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Applicability::MachineApplicable,
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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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/// Tries to determine the type for universal function call to be used instead of the closure
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fn get_ufcs_type_name(
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cx: &LateContext<'_, '_>,
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method_def_id: def_id::DefId,
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self_arg: &Expr,
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) -> std::option::Option<String> {
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let expected_type_of_self = &cx.tcx.fn_sig(method_def_id).inputs_and_output().skip_binder()[0].sty;
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2019-02-13 15:06:19 -06:00
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let actual_type_of_self = &cx.tables.node_type(self_arg.hir_id).sty;
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if let Some(trait_id) = cx.tcx.trait_of_item(method_def_id) {
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2019-02-26 05:12:27 -06:00
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if match_borrow_depth(expected_type_of_self, actual_type_of_self) {
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return Some(cx.tcx.item_path_str(trait_id));
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}
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2019-02-10 05:58:51 -06:00
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}
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cx.tcx.impl_of_method(method_def_id).and_then(|_| {
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2019-02-26 05:12:27 -06:00
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//a type may implicitly implement other type's methods (e.g. Deref)
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2019-02-10 05:58:51 -06:00
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if match_types(expected_type_of_self, actual_type_of_self) {
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return Some(get_type_name(cx, &actual_type_of_self));
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}
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None
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})
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}
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2019-02-26 05:12:27 -06:00
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fn match_borrow_depth(lhs: &ty::TyKind<'_>, rhs: &ty::TyKind<'_>) -> bool {
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match (lhs, rhs) {
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(ty::Ref(_, t1, _), ty::Ref(_, t2, _)) => match_borrow_depth(&t1.sty, &t2.sty),
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(l, r) => match (l, r) {
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(ty::Ref(_, _, _), _) | (_, ty::Ref(_, _, _)) => false,
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(_, _) => true,
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},
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}
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}
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2019-02-10 05:58:51 -06:00
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fn match_types(lhs: &ty::TyKind<'_>, rhs: &ty::TyKind<'_>) -> bool {
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match (lhs, rhs) {
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(ty::Bool, ty::Bool)
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| (ty::Char, ty::Char)
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| (ty::Int(_), ty::Int(_))
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| (ty::Uint(_), ty::Uint(_))
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| (ty::Str, ty::Str) => true,
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(ty::Ref(_, t1, _), ty::Ref(_, t2, _))
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| (ty::Array(t1, _), ty::Array(t2, _))
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| (ty::Slice(t1), ty::Slice(t2)) => match_types(&t1.sty, &t2.sty),
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(ty::Adt(def1, _), ty::Adt(def2, _)) => def1 == def2,
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(_, _) => false,
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}
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}
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fn get_type_name(cx: &LateContext<'_, '_>, kind: &ty::TyKind<'_>) -> String {
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match kind {
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ty::Adt(t, _) => cx.tcx.item_path_str(t.did),
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ty::Ref(_, r, _) => get_type_name(cx, &r.sty),
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_ => kind.to_string(),
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}
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}
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fn compare_inputs(closure_inputs: &mut dyn Iterator<Item = &Arg>, call_args: &mut dyn Iterator<Item = &Expr>) -> bool {
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for (closure_input, function_arg) in closure_inputs.zip(call_args) {
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2019-03-07 14:51:05 -06:00
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if let PatKind::Binding(_, _, ident, _) = closure_input.pat.node {
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2019-02-10 05:58:51 -06:00
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// XXXManishearth Should I be checking the binding mode here?
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if let ExprKind::Path(QPath::Resolved(None, ref p)) = function_arg.node {
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if p.segments.len() != 1 {
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// If it's a proper path, it can't be a local variable
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return false;
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}
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if p.segments[0].ident.name != ident.name {
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// The two idents should be the same
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return false;
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}
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} else {
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return false;
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}
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} else {
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return false;
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2015-05-10 00:09:04 -05:00
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}
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}
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2019-02-10 05:58:51 -06:00
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true
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}
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