2018-05-30 03:15:50 -05:00
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use crate::utils::ptr::get_spans;
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2018-11-27 14:14:15 -06:00
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use crate::utils::{
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2019-09-11 01:26:57 -05:00
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get_trait_def_id, implements_trait, is_copy, is_self, is_type_diagnostic_item, match_type, multispan_sugg, paths,
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snippet, snippet_opt, span_lint_and_then,
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2018-11-27 14:14:15 -06:00
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};
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use if_chain::if_chain;
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use matches::matches;
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2018-12-29 09:04:45 -06:00
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use rustc::hir::intravisit::FnKind;
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::middle::expr_use_visitor as euv;
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use rustc::middle::mem_categorization as mc;
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use rustc::traits;
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use rustc::ty::{self, RegionKind, TypeFoldable};
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2019-04-08 15:43:55 -05:00
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use rustc::{declare_lint_pass, declare_tool_lint};
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2018-12-29 09:04:45 -06:00
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
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use rustc_errors::Applicability;
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use rustc_target::spec::abi::Abi;
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2017-10-08 03:51:44 -05:00
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use std::borrow::Cow;
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2019-03-11 06:45:57 -05:00
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use syntax::ast::Attribute;
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2018-12-29 09:04:45 -06:00
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use syntax::errors::DiagnosticBuilder;
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2019-09-07 05:21:52 -05:00
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use syntax_pos::{Span, Symbol};
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2017-02-18 02:00:36 -06:00
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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 functions taking arguments by value, but not
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/// consuming them in its
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/// body.
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///
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/// **Why is this bad?** Taking arguments by reference is more flexible and can
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/// sometimes avoid
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/// unnecessary allocations.
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///
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/// **Known problems:**
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/// * This lint suggests taking an argument by reference,
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/// however sometimes it is better to let users decide the argument type
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/// (by using `Borrow` trait, for example), depending on how the function is used.
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///
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/// **Example:**
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/// ```rust
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/// fn foo(v: Vec<i32>) {
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/// assert_eq!(v.len(), 42);
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/// }
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2019-08-03 11:42:05 -05:00
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/// ```
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///
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/// ```rust
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2019-03-05 10:50:33 -06:00
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/// // should be
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/// fn foo(v: &[i32]) {
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/// assert_eq!(v.len(), 42);
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/// }
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/// ```
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2017-02-19 21:50:31 -06:00
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pub NEEDLESS_PASS_BY_VALUE,
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2018-11-21 03:58:27 -06:00
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pedantic,
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2017-02-19 21:50:31 -06:00
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"functions taking arguments by value, but not consuming them in its body"
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2017-02-18 02:00:36 -06:00
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}
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2019-04-08 15:43:55 -05:00
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declare_lint_pass!(NeedlessPassByValue => [NEEDLESS_PASS_BY_VALUE]);
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2017-02-18 02:00:36 -06:00
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2017-03-16 02:57:17 -05:00
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macro_rules! need {
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2018-11-27 14:14:15 -06:00
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($e: expr) => {
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if let Some(x) = $e {
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x
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} else {
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return;
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}
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};
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2017-03-16 02:57:17 -05:00
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}
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2017-02-19 21:50:31 -06:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessPassByValue {
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2019-01-13 09:19:02 -06:00
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#[allow(clippy::too_many_lines)]
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2017-02-18 02:00:36 -06:00
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fn check_fn(
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&mut self,
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cx: &LateContext<'a, 'tcx>,
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kind: FnKind<'tcx>,
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decl: &'tcx FnDecl,
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body: &'tcx Body,
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span: Span,
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2019-02-20 04:11:11 -06:00
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hir_id: HirId,
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2017-02-18 02:00:36 -06:00
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) {
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2019-08-19 11:30:32 -05:00
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if span.from_expansion() {
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2017-02-18 02:00:36 -06:00
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return;
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}
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2017-03-12 17:30:18 -05:00
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match kind {
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2018-06-24 08:32:40 -05:00
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FnKind::ItemFn(.., header, _, attrs) => {
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2019-03-11 06:45:57 -05:00
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if header.abi != Abi::Rust || requires_exact_signature(attrs) {
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2018-01-18 02:30:52 -06:00
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return;
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}
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2017-03-12 17:30:18 -05:00
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},
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2017-11-03 03:24:10 -05:00
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FnKind::Method(..) => (),
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2017-03-12 17:30:18 -05:00
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_ => return,
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2017-02-18 02:00:36 -06:00
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}
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2017-11-03 03:24:10 -05:00
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// Exclude non-inherent impls
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2019-06-25 16:41:10 -05:00
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if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
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2019-09-27 10:16:06 -05:00
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if matches!(item.kind, ItemKind::Impl(_, _, _, _, Some(_), _, _) |
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2018-07-16 08:07:39 -05:00
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ItemKind::Trait(..))
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2017-11-06 15:33:25 -06:00
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{
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2017-11-03 03:24:10 -05:00
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return;
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}
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}
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2017-10-08 04:04:45 -05:00
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// Allow `Borrow` or functions to be taken by value
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2019-05-17 16:53:54 -05:00
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let borrow_trait = need!(get_trait_def_id(cx, &paths::BORROW_TRAIT));
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2018-01-18 02:49:19 -06:00
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let whitelisted_traits = [
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2017-10-08 04:04:45 -05:00
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need!(cx.tcx.lang_items().fn_trait()),
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need!(cx.tcx.lang_items().fn_once_trait()),
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need!(cx.tcx.lang_items().fn_mut_trait()),
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2019-05-17 16:53:54 -05:00
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need!(get_trait_def_id(cx, &paths::RANGE_ARGUMENT_TRAIT)),
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2017-10-08 04:04:45 -05:00
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];
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2017-10-07 20:23:41 -05:00
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let sized_trait = need!(cx.tcx.lang_items().sized_trait());
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2017-02-18 02:00:36 -06:00
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2019-07-05 22:52:51 -05:00
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let fn_def_id = cx.tcx.hir().local_def_id(hir_id);
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2017-05-14 02:56:10 -05:00
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2017-10-07 20:23:41 -05:00
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let preds = traits::elaborate_predicates(cx.tcx, cx.param_env.caller_bounds.to_vec())
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.filter(|p| !p.is_global())
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2017-11-04 14:55:56 -05:00
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.filter_map(|pred| {
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if let ty::Predicate::Trait(poly_trait_ref) = pred {
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2018-11-27 14:14:15 -06:00
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if poly_trait_ref.def_id() == sized_trait || poly_trait_ref.skip_binder().has_escaping_bound_vars()
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{
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2017-11-04 14:55:56 -05:00
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return None;
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}
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Some(poly_trait_ref)
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} else {
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None
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2017-10-08 06:17:04 -05:00
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}
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2017-10-07 20:23:41 -05:00
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})
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.collect::<Vec<_>>();
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2017-02-19 21:50:31 -06:00
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2017-08-09 02:30:56 -05:00
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// Collect moved variables and spans which will need dereferencings from the
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// function body.
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let MovedVariablesCtxt {
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moved_vars,
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spans_need_deref,
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..
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} = {
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2019-10-04 08:00:01 -05:00
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let mut ctx = MovedVariablesCtxt::default();
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2017-09-04 09:10:36 -05:00
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let region_scope_tree = &cx.tcx.region_scope_tree(fn_def_id);
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2019-10-05 05:42:09 -05:00
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euv::ExprUseVisitor::new(&mut ctx, cx.tcx, fn_def_id, cx.param_env, region_scope_tree, cx.tables)
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.consume_body(body);
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2017-02-20 01:45:37 -06:00
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ctx
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2017-02-18 02:00:36 -06:00
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};
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2017-06-29 08:38:25 -05:00
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let fn_sig = cx.tcx.fn_sig(fn_def_id);
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2017-05-14 02:56:10 -05:00
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let fn_sig = cx.tcx.erase_late_bound_regions(&fn_sig);
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2017-02-18 02:00:36 -06:00
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2019-08-28 04:27:06 -05:00
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for (idx, ((input, &ty), arg)) in decl.inputs.iter().zip(fn_sig.inputs()).zip(&body.params).enumerate() {
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2017-10-17 17:29:47 -05:00
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// All spans generated from a proc-macro invocation are the same...
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if span == input.span {
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return;
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}
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2017-11-03 03:24:10 -05:00
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// Ignore `self`s.
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if idx == 0 {
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2019-09-27 10:16:06 -05:00
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if let PatKind::Binding(.., ident, _) = arg.pat.kind {
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2018-06-28 08:46:58 -05:00
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if ident.as_str() == "self" {
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2017-11-03 03:24:10 -05:00
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continue;
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}
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}
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}
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2018-11-27 14:14:15 -06:00
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//
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2017-10-07 20:23:41 -05:00
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// * Exclude a type that is specifically bounded by `Borrow`.
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2019-01-30 19:15:29 -06:00
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// * Exclude a type whose reference also fulfills its bound. (e.g., `std::convert::AsRef`,
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2018-11-27 14:14:15 -06:00
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// `serde::Serialize`)
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2017-10-07 20:23:41 -05:00
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let (implements_borrow_trait, all_borrowable_trait) = {
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let preds = preds
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.iter()
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2017-10-08 06:17:04 -05:00
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.filter(|t| t.skip_binder().self_ty() == ty)
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2017-10-07 20:23:41 -05:00
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.collect::<Vec<_>>();
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(
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preds.iter().any(|t| t.def_id() == borrow_trait),
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2018-11-27 14:14:15 -06:00
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!preds.is_empty()
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&& preds.iter().all(|t| {
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let ty_params = &t
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.skip_binder()
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.trait_ref
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.substs
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.iter()
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.skip(1)
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.cloned()
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.collect::<Vec<_>>();
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2019-02-06 01:09:56 -06:00
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implements_trait(cx, cx.tcx.mk_imm_ref(&RegionKind::ReEmpty, ty), t.def_id(), ty_params)
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2018-11-27 14:14:15 -06:00
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}),
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2017-10-07 20:23:41 -05:00
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)
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};
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2017-02-19 21:50:31 -06:00
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2017-10-23 14:18:02 -05:00
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if_chain! {
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if !is_self(arg);
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2019-07-26 15:58:31 -05:00
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if !ty.is_mutable_ptr();
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2017-10-23 14:18:02 -05:00
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if !is_copy(cx, ty);
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2018-01-18 02:49:19 -06:00
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if !whitelisted_traits.iter().any(|&t| implements_trait(cx, ty, t, &[]));
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2017-10-23 14:18:02 -05:00
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if !implements_borrow_trait;
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if !all_borrowable_trait;
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2019-09-27 10:16:06 -05:00
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if let PatKind::Binding(mode, canonical_id, ..) = arg.pat.kind;
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2017-10-23 14:18:02 -05:00
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if !moved_vars.contains(&canonical_id);
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then {
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if mode == BindingAnnotation::Mutable || mode == BindingAnnotation::RefMut {
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continue;
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}
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2017-11-03 03:24:10 -05:00
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2017-10-23 14:18:02 -05:00
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// Dereference suggestion
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2018-07-23 06:01:12 -05:00
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let sugg = |db: &mut DiagnosticBuilder<'_>| {
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2019-09-26 04:03:36 -05:00
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if let ty::Adt(def, ..) = ty.kind {
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2018-12-07 18:56:03 -06:00
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if let Some(span) = cx.tcx.hir().span_if_local(def.did) {
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2018-05-21 10:45:48 -05:00
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if cx.param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
|
2018-01-18 07:27:47 -06:00
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db.span_help(span, "consider marking this type as Copy");
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}
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2018-01-18 02:45:41 -06:00
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}
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}
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2017-10-23 14:18:02 -05:00
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let deref_span = spans_need_deref.get(&canonical_id);
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if_chain! {
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2019-09-07 05:21:52 -05:00
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if is_type_diagnostic_item(cx, ty, Symbol::intern("vec_type"));
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2017-10-23 14:18:02 -05:00
|
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if let Some(clone_spans) =
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2019-05-17 16:53:54 -05:00
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get_spans(cx, Some(body.id()), idx, &[("clone", ".to_owned()")]);
|
2019-09-27 10:16:06 -05:00
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if let TyKind::Path(QPath::Resolved(_, ref path)) = input.kind;
|
2017-10-23 14:18:02 -05:00
|
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|
if let Some(elem_ty) = path.segments.iter()
|
2019-05-17 16:53:54 -05:00
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.find(|seg| seg.ident.name == sym!(Vec))
|
2018-06-24 08:32:40 -05:00
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.and_then(|ps| ps.args.as_ref())
|
2018-06-24 16:42:52 -05:00
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.map(|params| params.args.iter().find_map(|arg| match arg {
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|
GenericArg::Type(ty) => Some(ty),
|
2019-02-19 01:34:43 -06:00
|
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|
_ => None,
|
2018-06-24 16:42:52 -05:00
|
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|
}).unwrap());
|
2017-10-23 14:18:02 -05:00
|
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|
then {
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|
let slice_ty = format!("&[{}]", snippet(cx, elem_ty.span, "_"));
|
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
|
|
|
input.span,
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|
|
"consider changing the type to",
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|
|
slice_ty,
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|
Applicability::Unspecified,
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|
);
|
2017-11-03 03:24:10 -05:00
|
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|
2017-10-23 14:18:02 -05:00
|
|
|
for (span, suggestion) in clone_spans {
|
2019-01-27 06:33:56 -06:00
|
|
|
db.span_suggestion(
|
2017-10-23 14:18:02 -05:00
|
|
|
span,
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|
|
|
&snippet_opt(cx, span)
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|
|
|
.map_or(
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|
|
|
"change the call to".into(),
|
|
|
|
|x| Cow::from(format!("change `{}` to", x)),
|
|
|
|
),
|
2018-09-15 11:14:08 -05:00
|
|
|
suggestion.into(),
|
|
|
|
Applicability::Unspecified,
|
2017-10-23 14:18:02 -05:00
|
|
|
);
|
|
|
|
}
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2017-10-23 14:18:02 -05:00
|
|
|
// cannot be destructured, no need for `*` suggestion
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|
|
|
assert!(deref_span.is_none());
|
|
|
|
return;
|
|
|
|
}
|
2017-10-08 03:51:44 -05:00
|
|
|
}
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2019-05-17 16:53:54 -05:00
|
|
|
if match_type(cx, ty, &paths::STRING) {
|
2017-10-23 14:18:02 -05:00
|
|
|
if let Some(clone_spans) =
|
2019-05-17 16:53:54 -05:00
|
|
|
get_spans(cx, Some(body.id()), idx, &[("clone", ".to_string()"), ("as_str", "")]) {
|
2019-01-27 06:33:56 -06:00
|
|
|
db.span_suggestion(
|
2018-09-18 10:07:54 -05:00
|
|
|
input.span,
|
|
|
|
"consider changing the type to",
|
|
|
|
"&str".to_string(),
|
|
|
|
Applicability::Unspecified,
|
|
|
|
);
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2017-10-23 14:18:02 -05:00
|
|
|
for (span, suggestion) in clone_spans {
|
2019-01-27 06:33:56 -06:00
|
|
|
db.span_suggestion(
|
2017-10-23 14:18:02 -05:00
|
|
|
span,
|
|
|
|
&snippet_opt(cx, span)
|
|
|
|
.map_or(
|
|
|
|
"change the call to".into(),
|
|
|
|
|x| Cow::from(format!("change `{}` to", x))
|
|
|
|
),
|
|
|
|
suggestion.into(),
|
2018-09-15 11:14:08 -05:00
|
|
|
Applicability::Unspecified,
|
2017-10-23 14:18:02 -05:00
|
|
|
);
|
|
|
|
}
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2017-10-23 14:18:02 -05:00
|
|
|
assert!(deref_span.is_none());
|
|
|
|
return;
|
2017-10-08 03:51:44 -05:00
|
|
|
}
|
|
|
|
}
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2017-10-23 14:18:02 -05:00
|
|
|
let mut spans = vec![(input.span, format!("&{}", snippet(cx, input.span, "_")))];
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2017-10-23 14:18:02 -05:00
|
|
|
// Suggests adding `*` to dereference the added reference.
|
|
|
|
if let Some(deref_span) = deref_span {
|
|
|
|
spans.extend(
|
|
|
|
deref_span
|
|
|
|
.iter()
|
|
|
|
.cloned()
|
|
|
|
.map(|span| (span, format!("*{}", snippet(cx, span, "<expr>")))),
|
|
|
|
);
|
|
|
|
spans.sort_by_key(|&(span, _)| span);
|
|
|
|
}
|
|
|
|
multispan_sugg(db, "consider taking a reference instead".to_string(), spans);
|
|
|
|
};
|
2017-11-03 03:24:10 -05:00
|
|
|
|
2017-10-23 14:18:02 -05:00
|
|
|
span_lint_and_then(
|
|
|
|
cx,
|
|
|
|
NEEDLESS_PASS_BY_VALUE,
|
|
|
|
input.span,
|
|
|
|
"this argument is passed by value, but not consumed in the function body",
|
|
|
|
sugg,
|
|
|
|
);
|
|
|
|
}
|
|
|
|
}
|
2017-02-18 02:00:36 -06:00
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2019-03-11 06:45:57 -05:00
|
|
|
/// Functions marked with these attributes must have the exact signature.
|
|
|
|
fn requires_exact_signature(attrs: &[Attribute]) -> bool {
|
|
|
|
attrs.iter().any(|attr| {
|
2019-05-17 16:53:54 -05:00
|
|
|
[sym!(proc_macro), sym!(proc_macro_attribute), sym!(proc_macro_derive)]
|
2019-03-11 06:45:57 -05:00
|
|
|
.iter()
|
2019-03-18 06:15:23 -05:00
|
|
|
.any(|&allow| attr.check_name(allow))
|
2019-03-11 06:45:57 -05:00
|
|
|
})
|
|
|
|
}
|
|
|
|
|
2019-10-04 08:00:01 -05:00
|
|
|
#[derive(Default)]
|
|
|
|
struct MovedVariablesCtxt {
|
2019-03-01 06:26:06 -06:00
|
|
|
moved_vars: FxHashSet<HirId>,
|
2017-08-09 02:30:56 -05:00
|
|
|
/// Spans which need to be prefixed with `*` for dereferencing the
|
2017-10-07 20:23:41 -05:00
|
|
|
/// suggested additional reference.
|
2019-03-01 06:26:06 -06:00
|
|
|
spans_need_deref: FxHashMap<HirId, FxHashSet<Span>>,
|
2017-02-18 02:00:36 -06:00
|
|
|
}
|
|
|
|
|
2019-10-04 08:00:01 -05:00
|
|
|
impl MovedVariablesCtxt {
|
2019-11-28 09:09:02 -06:00
|
|
|
fn move_common(&mut self, cmt: &mc::Place<'_>) {
|
2017-02-20 01:45:37 -06:00
|
|
|
let cmt = unwrap_downcast_or_interior(cmt);
|
|
|
|
|
2017-09-12 07:26:40 -05:00
|
|
|
if let mc::Categorization::Local(vid) = cmt.cat {
|
|
|
|
self.moved_vars.insert(vid);
|
|
|
|
}
|
2017-02-18 02:00:36 -06:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2019-10-04 08:00:01 -05:00
|
|
|
impl<'tcx> euv::Delegate<'tcx> for MovedVariablesCtxt {
|
2019-11-28 09:09:02 -06:00
|
|
|
fn consume(&mut self, cmt: &mc::Place<'tcx>, mode: euv::ConsumeMode) {
|
2019-10-04 07:24:47 -05:00
|
|
|
if let euv::ConsumeMode::Move = mode {
|
2019-10-04 08:00:01 -05:00
|
|
|
self.move_common(cmt);
|
2017-02-20 01:45:37 -06:00
|
|
|
}
|
2017-02-18 02:00:36 -06:00
|
|
|
}
|
|
|
|
|
2019-11-28 09:09:02 -06:00
|
|
|
fn borrow(&mut self, _: &mc::Place<'tcx>, _: ty::BorrowKind) {}
|
2017-02-18 02:00:36 -06:00
|
|
|
|
2019-11-28 09:09:02 -06:00
|
|
|
fn mutate(&mut self, _: &mc::Place<'tcx>) {}
|
2017-02-18 02:00:36 -06:00
|
|
|
}
|
2017-02-20 01:45:37 -06:00
|
|
|
|
2019-11-28 09:09:02 -06:00
|
|
|
fn unwrap_downcast_or_interior<'a, 'tcx>(mut cmt: &'a mc::Place<'tcx>) -> mc::Place<'tcx> {
|
2017-02-20 01:45:37 -06:00
|
|
|
loop {
|
2018-05-06 07:05:41 -05:00
|
|
|
match cmt.cat {
|
|
|
|
mc::Categorization::Downcast(ref c, _) | mc::Categorization::Interior(ref c, _) => {
|
2017-02-20 01:45:37 -06:00
|
|
|
cmt = c;
|
|
|
|
},
|
2018-05-06 07:05:41 -05:00
|
|
|
_ => return (*cmt).clone(),
|
2017-02-20 01:45:37 -06:00
|
|
|
}
|
2018-11-27 14:14:15 -06:00
|
|
|
}
|
2017-02-20 01:45:37 -06:00
|
|
|
}
|