| use crate::utils::{match_def_path, paths, snippet, span_lint_and_then, walk_ptrs_ty_depth}; |
| use if_chain::if_chain; |
| use rustc::hir::{Expr, ExprKind}; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::{declare_lint_pass, declare_tool_lint}; |
| use rustc_errors::Applicability; |
| |
| use std::iter; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for calls of `mem::discriminant()` on a non-enum type. |
| /// |
| /// **Why is this bad?** The value of `mem::discriminant()` on non-enum types |
| /// is unspecified. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// use std::mem; |
| /// |
| /// mem::discriminant(&"hello"); |
| /// mem::discriminant(&&Some(2)); |
| /// ``` |
| pub MEM_DISCRIMINANT_NON_ENUM, |
| correctness, |
| "calling mem::descriminant on non-enum type" |
| } |
| |
| declare_lint_pass!(MemDiscriminant => [MEM_DISCRIMINANT_NON_ENUM]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemDiscriminant { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { |
| if_chain! { |
| if let ExprKind::Call(ref func, ref func_args) = expr.kind; |
| // is `mem::discriminant` |
| if let ExprKind::Path(ref func_qpath) = func.kind; |
| if let Some(def_id) = cx.tables.qpath_res(func_qpath, func.hir_id).opt_def_id(); |
| if match_def_path(cx, def_id, &paths::MEM_DISCRIMINANT); |
| // type is non-enum |
| let ty_param = cx.tables.node_substs(func.hir_id).type_at(0); |
| if !ty_param.is_enum(); |
| |
| then { |
| span_lint_and_then( |
| cx, |
| MEM_DISCRIMINANT_NON_ENUM, |
| expr.span, |
| &format!("calling `mem::discriminant` on non-enum type `{}`", ty_param), |
| |db| { |
| // if this is a reference to an enum, suggest dereferencing |
| let (base_ty, ptr_depth) = walk_ptrs_ty_depth(ty_param); |
| if ptr_depth >= 1 && base_ty.is_enum() { |
| let param = &func_args[0]; |
| |
| // cancel out '&'s first |
| let mut derefs_needed = ptr_depth; |
| let mut cur_expr = param; |
| while derefs_needed > 0 { |
| if let ExprKind::AddrOf(_, ref inner_expr) = cur_expr.kind { |
| derefs_needed -= 1; |
| cur_expr = inner_expr; |
| } else { |
| break; |
| } |
| } |
| |
| let derefs: String = iter::repeat('*').take(derefs_needed).collect(); |
| db.span_suggestion( |
| param.span, |
| "try dereferencing", |
| format!("{}{}", derefs, snippet(cx, cur_expr.span, "<param>")), |
| Applicability::MachineApplicable, |
| ); |
| } |
| }, |
| ) |
| } |
| } |
| } |
| } |