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| 1 | +use rustc_hir::attrs::AttributeKind; |
| 2 | +use rustc_hir::def::{DefKind, Res}; |
| 3 | +use rustc_hir::{Expr, ExprKind, ItemKind, Node, find_attr}; |
| 4 | +use rustc_session::{declare_lint, declare_lint_pass}; |
| 5 | + |
| 6 | +use crate::lints::{ConstItemInteriorMutationsDiag, ConstItemInteriorMutationsSuggestionStatic}; |
| 7 | +use crate::{LateContext, LateLintPass, LintContext}; |
| 8 | + |
| 9 | +declare_lint! { |
| 10 | + /// The `const_item_interior_mutations` lint checks for calls which |
| 11 | + /// mutates an interior mutable const-item. |
| 12 | + /// |
| 13 | + /// ### Example |
| 14 | + /// |
| 15 | + /// ```rust |
| 16 | + /// use std::sync::Once; |
| 17 | + /// |
| 18 | + /// const INIT: Once = Once::new(); // using `INIT` will always create a temporary and |
| 19 | + /// // never modify it-self on use, should be a `static` |
| 20 | + /// // instead for shared use |
| 21 | + /// |
| 22 | + /// fn init() { |
| 23 | + /// INIT.call_once(|| { |
| 24 | + /// println!("Once::call_once first call"); |
| 25 | + /// }); |
| 26 | + /// INIT.call_once(|| { // this second will also print |
| 27 | + /// println!("Once::call_once second call"); // as each call to `INIT` creates |
| 28 | + /// }); // new temporary |
| 29 | + /// } |
| 30 | + /// ``` |
| 31 | + /// |
| 32 | + /// {{produces}} |
| 33 | + /// |
| 34 | + /// ### Explanation |
| 35 | + /// |
| 36 | + /// Calling a method which mutates an interior mutable type has no effect as const-item |
| 37 | + /// are essentially inlined wherever they are used, meaning that they are copied |
| 38 | + /// directly into the relevant context when used rendering modification through |
| 39 | + /// interior mutability ineffective across usage of that const-item. |
| 40 | + /// |
| 41 | + /// The current implementation of this lint only warns on significant `std` and |
| 42 | + /// `core` interior mutable types, like `Once`, `AtomicI32`, ... this is done out |
| 43 | + /// of prudence to avoid false-positive and may be extended in the future. |
| 44 | + pub CONST_ITEM_INTERIOR_MUTATIONS, |
| 45 | + Warn, |
| 46 | + "checks for calls which mutates a interior mutable const-item" |
| 47 | +} |
| 48 | + |
| 49 | +declare_lint_pass!(InteriorMutableConsts => [CONST_ITEM_INTERIOR_MUTATIONS]); |
| 50 | + |
| 51 | +impl<'tcx> LateLintPass<'tcx> for InteriorMutableConsts { |
| 52 | + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { |
| 53 | + let typeck = cx.typeck_results(); |
| 54 | + |
| 55 | + let (method_did, receiver) = match expr.kind { |
| 56 | + // matching on `<receiver>.method(..)` |
| 57 | + ExprKind::MethodCall(_, receiver, _, _) => { |
| 58 | + (typeck.type_dependent_def_id(expr.hir_id), receiver) |
| 59 | + } |
| 60 | + // matching on `function(&<receiver>, ...)` |
| 61 | + ExprKind::Call(path, [receiver, ..]) => match receiver.kind { |
| 62 | + ExprKind::AddrOf(_, _, receiver) => match path.kind { |
| 63 | + ExprKind::Path(ref qpath) => { |
| 64 | + (cx.qpath_res(qpath, path.hir_id).opt_def_id(), receiver) |
| 65 | + } |
| 66 | + _ => return, |
| 67 | + }, |
| 68 | + _ => return, |
| 69 | + }, |
| 70 | + _ => return, |
| 71 | + }; |
| 72 | + |
| 73 | + let Some(method_did) = method_did else { |
| 74 | + return; |
| 75 | + }; |
| 76 | + |
| 77 | + if let ExprKind::Path(qpath) = &receiver.kind |
| 78 | + && let Res::Def(DefKind::Const | DefKind::AssocConst, const_did) = |
| 79 | + typeck.qpath_res(qpath, receiver.hir_id) |
| 80 | + // Let's do the attribute check after the other checks for perf reasons |
| 81 | + && find_attr!( |
| 82 | + cx.tcx.get_all_attrs(method_did), |
| 83 | + AttributeKind::RustcShouldNotBeCalledOnConstItems(_) |
| 84 | + ) |
| 85 | + && let Some(method_name) = cx.tcx.opt_item_ident(method_did) |
| 86 | + && let Some(const_name) = cx.tcx.opt_item_ident(const_did) |
| 87 | + && let Some(const_ty) = typeck.node_type_opt(receiver.hir_id) |
| 88 | + { |
| 89 | + // Find the local `const`-item and create the suggestion to use `static` instead |
| 90 | + let sugg_static = if let Some(Node::Item(const_item)) = |
| 91 | + cx.tcx.hir_get_if_local(const_did) |
| 92 | + && let ItemKind::Const(ident, _generics, _ty, _body_id) = const_item.kind |
| 93 | + { |
| 94 | + if let Some(vis_span) = const_item.vis_span.find_ancestor_inside(const_item.span) |
| 95 | + && const_item.span.can_be_used_for_suggestions() |
| 96 | + && vis_span.can_be_used_for_suggestions() |
| 97 | + { |
| 98 | + Some(ConstItemInteriorMutationsSuggestionStatic::Spanful { |
| 99 | + const_: const_item.vis_span.between(ident.span), |
| 100 | + before: if !vis_span.is_empty() { " " } else { "" }, |
| 101 | + }) |
| 102 | + } else { |
| 103 | + Some(ConstItemInteriorMutationsSuggestionStatic::Spanless) |
| 104 | + } |
| 105 | + } else { |
| 106 | + None |
| 107 | + }; |
| 108 | + |
| 109 | + cx.emit_span_lint( |
| 110 | + CONST_ITEM_INTERIOR_MUTATIONS, |
| 111 | + expr.span, |
| 112 | + ConstItemInteriorMutationsDiag { |
| 113 | + method_name, |
| 114 | + const_name, |
| 115 | + const_ty, |
| 116 | + receiver_span: receiver.span, |
| 117 | + sugg_static, |
| 118 | + }, |
| 119 | + ); |
| 120 | + } |
| 121 | + } |
| 122 | +} |
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