1 use rustc_errors::Applicability;
2 use rustc_hir::{BinOpKind, Expr, ExprKind};
3 use rustc_lint::{LateContext, LateLintPass, LintContext};
4 use rustc_middle::lint::in_external_macro;
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
6 use rustc_span::source_map::Spanned;
8 use if_chain::if_chain;
10 use crate::utils::SpanlessEq;
11 use crate::utils::{get_parent_expr, is_allowed, is_type_diagnostic_item, span_lint, span_lint_and_sugg, walk_ptrs_ty};
13 declare_clippy_lint! {
14 /// **What it does:** Checks for string appends of the form `x = x + y` (without
17 /// **Why is this bad?** It's not really bad, but some people think that the
18 /// `.push_str(_)` method is more readable.
20 /// **Known problems:** None.
25 /// let mut x = "Hello".to_owned();
26 /// x = x + ", World";
30 /// x.push_str(", World");
32 pub STRING_ADD_ASSIGN,
34 "using `x = x + ..` where x is a `String` instead of `push_str()`"
37 declare_clippy_lint! {
38 /// **What it does:** Checks for all instances of `x + _` where `x` is of type
39 /// `String`, but only if [`string_add_assign`](#string_add_assign) does *not*
42 /// **Why is this bad?** It's not bad in and of itself. However, this particular
43 /// `Add` implementation is asymmetric (the other operand need not be `String`,
44 /// but `x` does), while addition as mathematically defined is symmetric, also
45 /// the `String::push_str(_)` function is a perfectly good replacement.
46 /// Therefore, some dislike it and wish not to have it in their code.
48 /// That said, other people think that string addition, having a long tradition
49 /// in other languages is actually fine, which is why we decided to make this
50 /// particular lint `allow` by default.
52 /// **Known problems:** None.
57 /// let x = "Hello".to_owned();
62 "using `x + ..` where x is a `String` instead of `push_str()`"
65 declare_clippy_lint! {
66 /// **What it does:** Checks for the `as_bytes` method called on string literals
67 /// that contain only ASCII characters.
69 /// **Why is this bad?** Byte string literals (e.g., `b"foo"`) can be used
70 /// instead. They are shorter but less discoverable than `as_bytes()`.
72 /// **Known Problems:** None.
77 /// let bs = "a byte string".as_bytes();
80 /// let bs = b"a byte string";
82 pub STRING_LIT_AS_BYTES,
84 "calling `as_bytes` on a string literal instead of using a byte string literal"
87 declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN]);
89 impl<'tcx> LateLintPass<'tcx> for StringAdd {
90 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
91 if in_external_macro(cx.sess(), e.span) {
95 if let ExprKind::Binary(
97 node: BinOpKind::Add, ..
103 if is_string(cx, left) {
104 if !is_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
105 let parent = get_parent_expr(cx, e);
106 if let Some(p) = parent {
107 if let ExprKind::Assign(ref target, _, _) = p.kind {
108 // avoid duplicate matches
109 if SpanlessEq::new(cx).eq_expr(target, left) {
119 "you added something to a string. Consider using `String::push_str()` instead",
122 } else if let ExprKind::Assign(ref target, ref src, _) = e.kind {
123 if is_string(cx, target) && is_add(cx, src, target) {
128 "you assigned the result of adding something to this string. Consider using \
129 `String::push_str()` instead",
136 fn is_string(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
137 is_type_diagnostic_item(cx, walk_ptrs_ty(cx.typeck_results().expr_ty(e)), sym!(string_type))
140 fn is_add(cx: &LateContext<'_>, src: &Expr<'_>, target: &Expr<'_>) -> bool {
144 node: BinOpKind::Add, ..
148 ) => SpanlessEq::new(cx).eq_expr(target, left),
149 ExprKind::Block(ref block, _) => {
150 block.stmts.is_empty() && block.expr.as_ref().map_or(false, |expr| is_add(cx, expr, target))
156 // Max length a b"foo" string can take
157 const MAX_LENGTH_BYTE_STRING_LIT: usize = 32;
159 declare_lint_pass!(StringLitAsBytes => [STRING_LIT_AS_BYTES]);
161 impl<'tcx> LateLintPass<'tcx> for StringLitAsBytes {
162 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
163 use crate::utils::{snippet, snippet_with_applicability};
164 use rustc_ast::ast::LitKind;
167 if let ExprKind::MethodCall(path, _, args, _) = &e.kind;
168 if path.ident.name == sym!(as_bytes);
169 if let ExprKind::Lit(lit) = &args[0].kind;
170 if let LitKind::Str(lit_content, _) = &lit.node;
172 let callsite = snippet(cx, args[0].span.source_callsite(), r#""foo""#);
173 let mut applicability = Applicability::MachineApplicable;
174 if callsite.starts_with("include_str!") {
179 "calling `as_bytes()` on `include_str!(..)`",
180 "consider using `include_bytes!(..)` instead",
181 snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability).replacen(
188 } else if lit_content.as_str().is_ascii()
189 && lit_content.as_str().len() <= MAX_LENGTH_BYTE_STRING_LIT
190 && !args[0].span.from_expansion()
196 "calling `as_bytes()` on a string literal",
197 "consider using a byte string literal instead",
200 snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability)