src/tools/clippy/clippy_lints/src/methods/seek_from_current.rs

   1 use rustc_ast::ast::{LitIntType, LitKind};
   2 use rustc_errors::Applicability;
   3 use rustc_hir::{Expr, ExprKind};
   4 use rustc_lint::LateContext;
   5
   6 use clippy_utils::{
   7     diagnostics::span_lint_and_sugg, get_trait_def_id, match_def_path, paths, source::snippet_with_applicability,
   8     ty::implements_trait,
   9 };
  10
  11 use super::SEEK_FROM_CURRENT;
  12
  13 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'tcx Expr<'_>, arg: &'tcx Expr<'_>) {
  14     let ty = cx.typeck_results().expr_ty(recv);
  15
  16     if let Some(def_id) = get_trait_def_id(cx, &paths::STD_IO_SEEK) {
  17         if implements_trait(cx, ty, def_id, &[]) && arg_is_seek_from_current(cx, arg) {
  18             let mut applicability = Applicability::MachineApplicable;
  19             let snip = snippet_with_applicability(cx, recv.span, "..", &mut applicability);
  20
  21             span_lint_and_sugg(
  22                 cx,
  23                 SEEK_FROM_CURRENT,
  24                 expr.span,
  25                 "using `SeekFrom::Current` to start from current position",
  26                 "replace with",
  27                 format!("{snip}.stream_position()"),
  28                 applicability,
  29             );
  30         }
  31     }
  32 }
  33
  34 fn arg_is_seek_from_current<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
  35     if let ExprKind::Call(f, args) = expr.kind &&
  36         let ExprKind::Path(ref path) = f.kind &&
  37         let Some(def_id) = cx.qpath_res(path, f.hir_id).opt_def_id() &&
  38         match_def_path(cx, def_id, &paths::STD_IO_SEEK_FROM_CURRENT) {
  39         // check if argument of `SeekFrom::Current` is `0`
  40         if args.len() == 1 &&
  41             let ExprKind::Lit(ref lit) = args[0].kind &&
  42             let LitKind::Int(0, LitIntType::Unsuffixed) = lit.node {
  43             return true
  44         }
  45     }
  46
  47     false
  48 }