1 use rustc::lint::in_external_macro;
2 use rustc_errors::Applicability;
4 use rustc_lint::{LateContext, LateLintPass, LintContext};
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, match_type, paths, 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";
28 pub STRING_ADD_ASSIGN,
30 "using `x = x + ..` where x is a `String` instead of `push_str()`"
33 declare_clippy_lint! {
34 /// **What it does:** Checks for all instances of `x + _` where `x` is of type
35 /// `String`, but only if [`string_add_assign`](#string_add_assign) does *not*
38 /// **Why is this bad?** It's not bad in and of itself. However, this particular
39 /// `Add` implementation is asymmetric (the other operand need not be `String`,
40 /// but `x` does), while addition as mathematically defined is symmetric, also
41 /// the `String::push_str(_)` function is a perfectly good replacement.
42 /// Therefore, some dislike it and wish not to have it in their code.
44 /// That said, other people think that string addition, having a long tradition
45 /// in other languages is actually fine, which is why we decided to make this
46 /// particular lint `allow` by default.
48 /// **Known problems:** None.
53 /// let x = "Hello".to_owned();
58 "using `x + ..` where x is a `String` instead of `push_str()`"
61 declare_clippy_lint! {
62 /// **What it does:** Checks for the `as_bytes` method called on string literals
63 /// that contain only ASCII characters.
65 /// **Why is this bad?** Byte string literals (e.g., `b"foo"`) can be used
66 /// instead. They are shorter but less discoverable than `as_bytes()`.
68 /// **Known Problems:** None.
72 /// let bs = "a byte string".as_bytes();
74 pub STRING_LIT_AS_BYTES,
76 "calling `as_bytes` on a string literal instead of using a byte string literal"
79 declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN]);
81 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringAdd {
82 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
83 if in_external_macro(cx.sess(), e.span) {
87 if let ExprKind::Binary(
89 node: BinOpKind::Add, ..
95 if is_string(cx, left) {
96 if !is_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
97 let parent = get_parent_expr(cx, e);
98 if let Some(p) = parent {
99 if let ExprKind::Assign(ref target, _, _) = p.kind {
100 // avoid duplicate matches
101 if SpanlessEq::new(cx).eq_expr(target, left) {
111 "you added something to a string. Consider using `String::push_str()` instead",
114 } else if let ExprKind::Assign(ref target, ref src, _) = e.kind {
115 if is_string(cx, target) && is_add(cx, src, target) {
120 "you assigned the result of adding something to this string. Consider using \
121 `String::push_str()` instead",
128 fn is_string(cx: &LateContext<'_, '_>, e: &Expr<'_>) -> bool {
129 match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(e)), &paths::STRING)
132 fn is_add(cx: &LateContext<'_, '_>, src: &Expr<'_>, target: &Expr<'_>) -> bool {
136 node: BinOpKind::Add, ..
140 ) => SpanlessEq::new(cx).eq_expr(target, left),
141 ExprKind::Block(ref block, _) => {
142 block.stmts.is_empty() && block.expr.as_ref().map_or(false, |expr| is_add(cx, expr, target))
148 // Max length a b"foo" string can take
149 const MAX_LENGTH_BYTE_STRING_LIT: usize = 32;
151 declare_lint_pass!(StringLitAsBytes => [STRING_LIT_AS_BYTES]);
153 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringLitAsBytes {
154 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
155 use crate::utils::{snippet, snippet_with_applicability};
156 use syntax::ast::LitKind;
159 if let ExprKind::MethodCall(path, _, args) = &e.kind;
160 if path.ident.name == sym!(as_bytes);
161 if let ExprKind::Lit(lit) = &args[0].kind;
162 if let LitKind::Str(lit_content, _) = &lit.node;
164 let callsite = snippet(cx, args[0].span.source_callsite(), r#""foo""#);
165 let mut applicability = Applicability::MachineApplicable;
166 if callsite.starts_with("include_str!") {
171 "calling `as_bytes()` on `include_str!(..)`",
172 "consider using `include_bytes!(..)` instead",
173 snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability).replacen(
180 } else if lit_content.as_str().is_ascii()
181 && lit_content.as_str().len() <= MAX_LENGTH_BYTE_STRING_LIT
182 && !args[0].span.from_expansion()
188 "calling `as_bytes()` on a string literal",
189 "consider using a byte string literal instead",
192 snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability)