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

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::ty::implements_trait;
   3 use clippy_utils::{get_trait_def_id, match_def_path, paths};
   4 use rustc_ast::ast::{LitIntType, LitKind};
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind};
   7 use rustc_lint::LateContext;
   8 use rustc_span::Span;
   9
  10 use super::SEEK_TO_START_INSTEAD_OF_REWIND;
  11
  12 pub(super) fn check<'tcx>(
  13     cx: &LateContext<'tcx>,
  14     expr: &'tcx Expr<'_>,
  15     recv: &'tcx Expr<'_>,
  16     arg: &'tcx Expr<'_>,
  17     name_span: Span,
  18 ) {
  19     // Get receiver type
  20     let ty = cx.typeck_results().expr_ty(recv).peel_refs();
  21
  22     if let Some(seek_trait_id) = get_trait_def_id(cx, &paths::STD_IO_SEEK) &&
  23         implements_trait(cx, ty, seek_trait_id, &[]) &&
  24         let ExprKind::Call(func, args1) = arg.kind &&
  25         let ExprKind::Path(ref path) = func.kind &&
  26         let Some(def_id) = cx.qpath_res(path, func.hir_id).opt_def_id() &&
  27         match_def_path(cx, def_id, &paths::STD_IO_SEEKFROM_START) &&
  28         args1.len() == 1 &&
  29         let ExprKind::Lit(ref lit) = args1[0].kind &&
  30         let LitKind::Int(0, LitIntType::Unsuffixed) = lit.node
  31     {
  32         let method_call_span = expr.span.with_lo(name_span.lo());
  33         span_lint_and_then(
  34             cx,
  35             SEEK_TO_START_INSTEAD_OF_REWIND,
  36             method_call_span,
  37             "used `seek` to go to the start of the stream",
  38             |diag| {
  39                 let app = Applicability::MachineApplicable;
  40
  41                 diag.span_suggestion(method_call_span, "replace with", "rewind()", app);
  42             },
  43         );
  44     }
  45 }