| use crate::lint::{LateContext, LateLintPass, LintArray, LintContext, LintPass}; |
| use rustc::{ |
| lint::FutureIncompatibleInfo, |
| hir, |
| ty::{ |
| self, |
| adjustment::{Adjust, Adjustment}, |
| }, |
| }; |
| use syntax::{ |
| errors::Applicability, |
| symbol::sym, |
| }; |
| |
| |
| declare_lint! { |
| pub ARRAY_INTO_ITER, |
| Warn, |
| "detects calling `into_iter` on arrays", |
| @future_incompatible = FutureIncompatibleInfo { |
| reference: "issue #66145 <https://github.com/rust-lang/rust/issues/66145>", |
| edition: None, |
| }; |
| } |
| |
| declare_lint_pass!( |
| /// Checks for instances of calling `into_iter` on arrays. |
| ArrayIntoIter => [ARRAY_INTO_ITER] |
| ); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ArrayIntoIter { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) { |
| // We only care about method call expressions. |
| if let hir::ExprKind::MethodCall(call, span, args) = &expr.kind { |
| if call.ident.name != sym::into_iter { |
| return; |
| } |
| |
| // Check if the method call actually calls the libcore |
| // `IntoIterator::into_iter`. |
| let def_id = cx.tables.type_dependent_def_id(expr.hir_id).unwrap(); |
| match cx.tcx.trait_of_item(def_id) { |
| Some(trait_id) if cx.tcx.is_diagnostic_item(sym::IntoIterator, trait_id) => {}, |
| _ => return, |
| }; |
| |
| // As this is a method call expression, we have at least one |
| // argument. |
| let receiver_arg = &args[0]; |
| |
| // Test if the original `self` type is an array type. |
| match cx.tables.expr_ty(receiver_arg).kind { |
| ty::Array(..) => {} |
| _ => return, |
| } |
| |
| // Make sure that the first adjustment is an autoref coercion. |
| match cx.tables.expr_adjustments(receiver_arg).get(0) { |
| Some(Adjustment { kind: Adjust::Borrow(_), .. }) => {} |
| _ => return, |
| } |
| |
| // Emit lint diagnostic. |
| let target = match cx.tables.expr_ty_adjusted(receiver_arg).kind { |
| ty::Ref(_, ty::TyS { kind: ty::Array(..), ..}, _) => "[T; N]", |
| ty::Ref(_, ty::TyS { kind: ty::Slice(..), ..}, _) => "[T]", |
| |
| // We know the original first argument type is an array type, |
| // we know that the first adjustment was an autoref coercion |
| // and we know that `IntoIterator` is the trait involved. The |
| // array cannot be coerced to something other than a reference |
| // to an array or to a slice. |
| _ => bug!("array type coerced to something other than array or slice"), |
| }; |
| let msg = format!( |
| "this method call currently resolves to `<&{} as IntoIterator>::into_iter` (due \ |
| to autoref coercions), but that might change in the future when \ |
| `IntoIterator` impls for arrays are added.", |
| target, |
| ); |
| cx.struct_span_lint(ARRAY_INTO_ITER, *span, &msg) |
| .span_suggestion( |
| call.ident.span, |
| "use `.iter()` instead of `.into_iter()` to avoid ambiguity", |
| "iter".into(), |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| } |
| } |