1 use clippy_utils::diagnostics::span_lint_and_help;
2 use clippy_utils::paths;
3 use clippy_utils::ty::match_type;
4 use if_chain::if_chain;
5 use rustc_hir::{Expr, ExprKind, QPath};
6 use rustc_lint::{LateContext, LateLintPass};
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 /// Checks for use of File::read_to_end and File::read_to_string.
13 /// ### Why is this bad?
14 /// `fs::{read, read_to_string}` provide the same functionality when `buf` is empty with fewer imports and no intermediate values.
15 /// See also: [fs::read docs](https://doc.rust-lang.org/std/fs/fn.read.html), [fs::read_to_string docs](https://doc.rust-lang.org/std/fs/fn.read_to_string.html)
19 /// # use std::io::Read;
20 /// # use std::fs::File;
21 /// let mut f = File::open("foo.txt").unwrap();
22 /// let mut bytes = Vec::new();
23 /// f.read_to_end(&mut bytes).unwrap();
25 /// Can be written more concisely as
28 /// let mut bytes = fs::read("foo.txt").unwrap();
30 #[clippy::version = "1.44.0"]
31 pub VERBOSE_FILE_READS,
33 "use of `File::read_to_end` or `File::read_to_string`"
36 declare_lint_pass!(VerboseFileReads => [VERBOSE_FILE_READS]);
38 impl<'tcx> LateLintPass<'tcx> for VerboseFileReads {
39 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
40 if is_file_read_to_end(cx, expr) {
45 "use of `File::read_to_end`",
47 "consider using `fs::read` instead",
49 } else if is_file_read_to_string(cx, expr) {
54 "use of `File::read_to_string`",
56 "consider using `fs::read_to_string` instead",
62 fn is_file_read_to_end<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
64 if let ExprKind::MethodCall(method_name, _, exprs, _) = expr.kind;
65 if method_name.ident.as_str() == "read_to_end";
66 if let ExprKind::Path(QPath::Resolved(None, _)) = &exprs[0].kind;
67 let ty = cx.typeck_results().expr_ty(&exprs[0]);
68 if match_type(cx, ty, &paths::FILE);
76 fn is_file_read_to_string<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
78 if let ExprKind::MethodCall(method_name, _, exprs, _) = expr.kind;
79 if method_name.ident.as_str() == "read_to_string";
80 if let ExprKind::Path(QPath::Resolved(None, _)) = &exprs[0].kind;
81 let ty = cx.typeck_results().expr_ty(&exprs[0]);
82 if match_type(cx, ty, &paths::FILE);