2 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
3 use rustc::{declare_lint_pass, declare_tool_lint};
4 use rustc_errors::Applicability;
5 use syntax::source_map::Spanned;
8 use crate::utils::SpanlessEq;
9 use crate::utils::{get_parent_expr, is_allowed, match_type, paths, span_lint, span_lint_and_sugg, walk_ptrs_ty};
11 declare_clippy_lint! {
12 /// **What it does:** Checks for string appends of the form `x = x + y` (without
15 /// **Why is this bad?** It's not really bad, but some people think that the
16 /// `.push_str(_)` method is more readable.
18 /// **Known problems:** None.
23 /// let mut x = "Hello".to_owned();
24 /// x = x + ", World";
26 pub STRING_ADD_ASSIGN,
28 "using `x = x + ..` where x is a `String` instead of `push_str()`"
31 declare_clippy_lint! {
32 /// **What it does:** Checks for all instances of `x + _` where `x` is of type
33 /// `String`, but only if [`string_add_assign`](#string_add_assign) does *not*
36 /// **Why is this bad?** It's not bad in and of itself. However, this particular
37 /// `Add` implementation is asymmetric (the other operand need not be `String`,
38 /// but `x` does), while addition as mathematically defined is symmetric, also
39 /// the `String::push_str(_)` function is a perfectly good replacement.
40 /// Therefore, some dislike it and wish not to have it in their code.
42 /// That said, other people think that string addition, having a long tradition
43 /// in other languages is actually fine, which is why we decided to make this
44 /// particular lint `allow` by default.
46 /// **Known problems:** None.
51 /// let x = "Hello".to_owned();
56 "using `x + ..` where x is a `String` instead of `push_str()`"
59 declare_clippy_lint! {
60 /// **What it does:** Checks for the `as_bytes` method called on string literals
61 /// that contain only ASCII characters.
63 /// **Why is this bad?** Byte string literals (e.g., `b"foo"`) can be used
64 /// instead. They are shorter but less discoverable than `as_bytes()`.
66 /// **Known Problems:** None.
70 /// let bs = "a byte string".as_bytes();
72 pub STRING_LIT_AS_BYTES,
74 "calling `as_bytes` on a string literal instead of using a byte string literal"
77 declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN]);
79 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringAdd {
80 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
81 if let ExprKind::Binary(
83 node: BinOpKind::Add, ..
89 if is_string(cx, left) {
90 if !is_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
91 let parent = get_parent_expr(cx, e);
92 if let Some(p) = parent {
93 if let ExprKind::Assign(ref target, _) = p.node {
94 // avoid duplicate matches
95 if SpanlessEq::new(cx).eq_expr(target, left) {
105 "you added something to a string. Consider using `String::push_str()` instead",
108 } else if let ExprKind::Assign(ref target, ref src) = e.node {
109 if is_string(cx, target) && is_add(cx, src, target) {
114 "you assigned the result of adding something to this string. Consider using \
115 `String::push_str()` instead",
122 fn is_string(cx: &LateContext<'_, '_>, e: &Expr) -> bool {
123 match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(e)), &*paths::STRING)
126 fn is_add(cx: &LateContext<'_, '_>, src: &Expr, target: &Expr) -> bool {
130 node: BinOpKind::Add, ..
134 ) => SpanlessEq::new(cx).eq_expr(target, left),
135 ExprKind::Block(ref block, _) => {
136 block.stmts.is_empty() && block.expr.as_ref().map_or(false, |expr| is_add(cx, expr, target))
142 declare_lint_pass!(StringLitAsBytes => [STRING_LIT_AS_BYTES]);
144 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringLitAsBytes {
145 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
146 use crate::utils::{in_macro_or_desugar, snippet, snippet_with_applicability};
147 use syntax::ast::{LitKind, StrStyle};
149 if let ExprKind::MethodCall(ref path, _, ref args) = e.node {
150 if path.ident.name == *sym::as_bytes {
151 if let ExprKind::Lit(ref lit) = args[0].node {
152 if let LitKind::Str(ref lit_content, style) = lit.node {
153 let callsite = snippet(cx, args[0].span.source_callsite(), r#""foo""#);
154 let expanded = if let StrStyle::Raw(n) = style {
155 let term = (0..n).map(|_| '#').collect::<String>();
156 format!("r{0}\"{1}\"{0}", term, lit_content.as_str())
158 format!("\"{}\"", lit_content.as_str())
160 let mut applicability = Applicability::MachineApplicable;
161 if callsite.starts_with("include_str!") {
166 "calling `as_bytes()` on `include_str!(..)`",
167 "consider using `include_bytes!(..)` instead",
168 snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability).replacen(
175 } else if callsite == expanded
176 && lit_content.as_str().chars().all(|c| c.is_ascii())
177 && !in_macro_or_desugar(args[0].span)
183 "calling `as_bytes()` on a string literal",
184 "consider using a byte string literal instead",
187 snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability)