| use crate::utils::{higher, span_lint}; |
| use rustc::hir; |
| use rustc::hir::intravisit; |
| use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass}; |
| use rustc::ty; |
| use rustc::{declare_lint_pass, declare_tool_lint}; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for instances of `mut mut` references. |
| /// |
| /// **Why is this bad?** Multiple `mut`s don't add anything meaningful to the |
| /// source. This is either a copy'n'paste error, or it shows a fundamental |
| /// misunderstanding of references. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = &mut &mut y; |
| /// ``` |
| pub MUT_MUT, |
| pedantic, |
| "usage of double-mut refs, e.g., `&mut &mut ...`" |
| } |
| |
| declare_lint_pass!(MutMut => [MUT_MUT]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutMut { |
| fn check_block(&mut self, cx: &LateContext<'a, 'tcx>, block: &'tcx hir::Block) { |
| intravisit::walk_block(&mut MutVisitor { cx }, block); |
| } |
| |
| fn check_ty(&mut self, cx: &LateContext<'a, 'tcx>, ty: &'tcx hir::Ty) { |
| use rustc::hir::intravisit::Visitor; |
| |
| MutVisitor { cx }.visit_ty(ty); |
| } |
| } |
| |
| pub struct MutVisitor<'a, 'tcx> { |
| cx: &'a LateContext<'a, 'tcx>, |
| } |
| |
| impl<'a, 'tcx> intravisit::Visitor<'tcx> for MutVisitor<'a, 'tcx> { |
| fn visit_expr(&mut self, expr: &'tcx hir::Expr) { |
| if in_external_macro(self.cx.sess(), expr.span) { |
| return; |
| } |
| |
| if let Some((_, arg, body)) = higher::for_loop(expr) { |
| // A `for` loop lowers to: |
| // ```rust |
| // match ::std::iter::Iterator::next(&mut iter) { |
| // // ^^^^ |
| // ``` |
| // Let's ignore the generated code. |
| intravisit::walk_expr(self, arg); |
| intravisit::walk_expr(self, body); |
| } else if let hir::ExprKind::AddrOf(hir::MutMutable, ref e) = expr.node { |
| if let hir::ExprKind::AddrOf(hir::MutMutable, _) = e.node { |
| span_lint( |
| self.cx, |
| MUT_MUT, |
| expr.span, |
| "generally you want to avoid `&mut &mut _` if possible", |
| ); |
| } else if let ty::Ref(_, _, hir::MutMutable) = self.cx.tables.expr_ty(e).sty { |
| span_lint( |
| self.cx, |
| MUT_MUT, |
| expr.span, |
| "this expression mutably borrows a mutable reference. Consider reborrowing", |
| ); |
| } |
| } |
| } |
| |
| fn visit_ty(&mut self, ty: &'tcx hir::Ty) { |
| if let hir::TyKind::Rptr( |
| _, |
| hir::MutTy { |
| ty: ref pty, |
| mutbl: hir::MutMutable, |
| }, |
| ) = ty.node |
| { |
| if let hir::TyKind::Rptr( |
| _, |
| hir::MutTy { |
| mutbl: hir::MutMutable, .. |
| }, |
| ) = pty.node |
| { |
| span_lint( |
| self.cx, |
| MUT_MUT, |
| ty.span, |
| "generally you want to avoid `&mut &mut _` if possible", |
| ); |
| } |
| } |
| |
| intravisit::walk_ty(self, ty); |
| } |
| fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> { |
| intravisit::NestedVisitorMap::None |
| } |
| } |