mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
200 lines
7.1 KiB
Rust
200 lines
7.1 KiB
Rust
use rustc::declare_lint_pass;
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use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
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use rustc_errors::Applicability;
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use rustc_hir::*;
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use rustc_session::declare_tool_lint;
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use rustc_span::source_map::Spanned;
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use if_chain::if_chain;
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use crate::utils::SpanlessEq;
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use crate::utils::{get_parent_expr, is_allowed, match_type, paths, span_lint, span_lint_and_sugg, walk_ptrs_ty};
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declare_clippy_lint! {
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/// **What it does:** Checks for string appends of the form `x = x + y` (without
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/// `let`!).
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///
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/// **Why is this bad?** It's not really bad, but some people think that the
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/// `.push_str(_)` method is more readable.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let mut x = "Hello".to_owned();
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/// x = x + ", World";
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/// ```
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pub STRING_ADD_ASSIGN,
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pedantic,
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"using `x = x + ..` where x is a `String` instead of `push_str()`"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for all instances of `x + _` where `x` is of type
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/// `String`, but only if [`string_add_assign`](#string_add_assign) does *not*
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/// match.
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///
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/// **Why is this bad?** It's not bad in and of itself. However, this particular
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/// `Add` implementation is asymmetric (the other operand need not be `String`,
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/// but `x` does), while addition as mathematically defined is symmetric, also
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/// the `String::push_str(_)` function is a perfectly good replacement.
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/// Therefore, some dislike it and wish not to have it in their code.
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///
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/// That said, other people think that string addition, having a long tradition
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/// in other languages is actually fine, which is why we decided to make this
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/// particular lint `allow` by default.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let x = "Hello".to_owned();
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/// x + ", World";
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/// ```
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pub STRING_ADD,
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restriction,
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"using `x + ..` where x is a `String` instead of `push_str()`"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for the `as_bytes` method called on string literals
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/// that contain only ASCII characters.
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///
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/// **Why is this bad?** Byte string literals (e.g., `b"foo"`) can be used
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/// instead. They are shorter but less discoverable than `as_bytes()`.
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///
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/// **Known Problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let bs = "a byte string".as_bytes();
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/// ```
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pub STRING_LIT_AS_BYTES,
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style,
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"calling `as_bytes` on a string literal instead of using a byte string literal"
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}
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declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringAdd {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
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if in_external_macro(cx.sess(), e.span) {
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return;
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}
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if let ExprKind::Binary(
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Spanned {
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node: BinOpKind::Add, ..
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},
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ref left,
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_,
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) = e.kind
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{
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if is_string(cx, left) {
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if !is_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
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let parent = get_parent_expr(cx, e);
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if let Some(p) = parent {
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if let ExprKind::Assign(ref target, _, _) = p.kind {
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// avoid duplicate matches
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if SpanlessEq::new(cx).eq_expr(target, left) {
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return;
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}
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}
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}
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}
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span_lint(
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cx,
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STRING_ADD,
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e.span,
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"you added something to a string. Consider using `String::push_str()` instead",
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);
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}
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} else if let ExprKind::Assign(ref target, ref src, _) = e.kind {
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if is_string(cx, target) && is_add(cx, src, target) {
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span_lint(
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cx,
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STRING_ADD_ASSIGN,
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e.span,
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"you assigned the result of adding something to this string. Consider using \
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`String::push_str()` instead",
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);
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}
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}
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}
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}
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fn is_string(cx: &LateContext<'_, '_>, e: &Expr<'_>) -> bool {
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match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(e)), &paths::STRING)
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}
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fn is_add(cx: &LateContext<'_, '_>, src: &Expr<'_>, target: &Expr<'_>) -> bool {
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match src.kind {
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ExprKind::Binary(
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Spanned {
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node: BinOpKind::Add, ..
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},
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ref left,
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_,
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) => SpanlessEq::new(cx).eq_expr(target, left),
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ExprKind::Block(ref block, _) => {
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block.stmts.is_empty() && block.expr.as_ref().map_or(false, |expr| is_add(cx, expr, target))
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},
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_ => false,
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}
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}
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// Max length a b"foo" string can take
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const MAX_LENGTH_BYTE_STRING_LIT: usize = 32;
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declare_lint_pass!(StringLitAsBytes => [STRING_LIT_AS_BYTES]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringLitAsBytes {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
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use crate::utils::{snippet, snippet_with_applicability};
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use syntax::ast::LitKind;
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if_chain! {
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if let ExprKind::MethodCall(path, _, args) = &e.kind;
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if path.ident.name == sym!(as_bytes);
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if let ExprKind::Lit(lit) = &args[0].kind;
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if let LitKind::Str(lit_content, _) = &lit.node;
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then {
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let callsite = snippet(cx, args[0].span.source_callsite(), r#""foo""#);
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let mut applicability = Applicability::MachineApplicable;
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if callsite.starts_with("include_str!") {
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span_lint_and_sugg(
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cx,
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STRING_LIT_AS_BYTES,
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e.span,
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"calling `as_bytes()` on `include_str!(..)`",
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"consider using `include_bytes!(..)` instead",
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snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability).replacen(
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"include_str",
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"include_bytes",
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1,
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),
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applicability,
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);
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} else if lit_content.as_str().is_ascii()
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&& lit_content.as_str().len() <= MAX_LENGTH_BYTE_STRING_LIT
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&& !args[0].span.from_expansion()
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{
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span_lint_and_sugg(
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cx,
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STRING_LIT_AS_BYTES,
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e.span,
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"calling `as_bytes()` on a string literal",
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"consider using a byte string literal instead",
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format!(
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"b{}",
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snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability)
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),
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applicability,
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);
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}
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}
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}
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}
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}
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