3 use syntax::codemap::Spanned;
5 use utils::{get_parent_expr, is_allowed, match_type, paths, span_lint, span_lint_and_sugg, walk_ptrs_ty};
7 /// **What it does:** Checks for string appends of the form `x = x + y` (without
10 /// **Why is this bad?** It's not really bad, but some people think that the
11 /// `.push_str(_)` method is more readable. Also creates a new heap allocation and throws
14 /// **Known problems:** None.
19 /// let mut x = "Hello".to_owned();
20 /// x = x + ", World";
22 declare_clippy_lint! {
23 pub STRING_ADD_ASSIGN,
25 "using `x = x + ..` where x is a `String` instead of `push_str()`"
28 /// **What it does:** Checks for all instances of `x + _` where `x` is of type
29 /// `String`, but only if [`string_add_assign`](#string_add_assign) does *not*
32 /// **Why is this bad?** It's not bad in and of itself. However, this particular
33 /// `Add` implementation is asymmetric (the other operand need not be `String`,
34 /// but `x` does), while addition as mathematically defined is symmetric, also
35 /// the `String::push_str(_)` function is a perfectly good replacement.
36 /// Therefore some dislike it and wish not to have it in their code.
38 /// That said, other people think that string addition, having a long tradition
39 /// in other languages is actually fine, which is why we decided to make this
40 /// particular lint `allow` by default.
42 /// **Known problems:** None.
47 /// let x = "Hello".to_owned();
50 declare_clippy_lint! {
53 "using `x + ..` where x is a `String` instead of `push_str()`"
56 /// **What it does:** Checks for the `as_bytes` method called on string literals
57 /// that contain only ASCII characters.
59 /// **Why is this bad?** Byte string literals (e.g. `b"foo"`) can be used
60 /// instead. They are shorter but less discoverable than `as_bytes()`.
62 /// **Known Problems:** None.
66 /// let bs = "a byte string".as_bytes();
68 declare_clippy_lint! {
69 pub STRING_LIT_AS_BYTES,
71 "calling `as_bytes` on a string literal instead of using a byte string literal"
74 #[derive(Copy, Clone)]
77 impl LintPass for StringAdd {
78 fn get_lints(&self) -> LintArray {
79 lint_array!(STRING_ADD, STRING_ADD_ASSIGN)
83 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringAdd {
84 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
85 if let ExprBinary(Spanned { node: BiAdd, .. }, ref left, _) = e.node {
86 if is_string(cx, left) {
87 if !is_allowed(cx, STRING_ADD_ASSIGN, e.id) {
88 let parent = get_parent_expr(cx, e);
89 if let Some(p) = parent {
90 if let ExprAssign(ref target, _) = p.node {
91 // avoid duplicate matches
92 if SpanlessEq::new(cx).eq_expr(target, left) {
102 "you added something to a string. Consider using `String::push_str()` instead",
105 } else if let ExprAssign(ref target, ref src) = e.node {
106 if is_string(cx, target) && is_add(cx, src, target) {
111 "you assigned the result of adding something to this string. Consider using \
112 `String::push_str()` instead",
119 fn is_string(cx: &LateContext, e: &Expr) -> bool {
120 match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(e)), &paths::STRING)
123 fn is_add(cx: &LateContext, src: &Expr, target: &Expr) -> bool {
125 ExprBinary(Spanned { node: BiAdd, .. }, ref left, _) => SpanlessEq::new(cx).eq_expr(target, left),
126 ExprBlock(ref block, _) => {
127 block.stmts.is_empty()
131 .map_or(false, |expr| is_add(cx, expr, target))
137 #[derive(Copy, Clone)]
138 pub struct StringLitAsBytes;
140 impl LintPass for StringLitAsBytes {
141 fn get_lints(&self) -> LintArray {
142 lint_array!(STRING_LIT_AS_BYTES)
146 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringLitAsBytes {
147 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
148 use syntax::ast::LitKind;
149 use utils::{in_macro, snippet};
151 if let ExprMethodCall(ref path, _, ref args) = e.node {
152 if path.name == "as_bytes" {
153 if let ExprLit(ref lit) = args[0].node {
154 if let LitKind::Str(ref lit_content, _) = lit.node {
155 if lit_content.as_str().chars().all(|c| c.is_ascii()) && !in_macro(args[0].span) {
160 "calling `as_bytes()` on a string literal",
161 "consider using a byte string literal instead",
162 format!("b{}", snippet(cx, args[0].span, r#""foo""#)),