389 lines
14 KiB
Rust
389 lines
14 KiB
Rust
use rustc_errors::Applicability;
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use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, LangItem, QPath};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_middle::ty;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Spanned;
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use rustc_span::sym;
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use if_chain::if_chain;
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use crate::utils::SpanlessEq;
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use crate::utils::{
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get_parent_expr, is_allowed, is_type_diagnostic_item, match_function_call, method_calls, paths, span_lint,
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span_lint_and_help, span_lint_and_sugg,
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};
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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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/// // More readable
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/// x += ", World";
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/// x.push_str(", 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:**
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/// `"str".as_bytes()` and the suggested replacement of `b"str"` are not
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/// equivalent because they have different types. The former is `&[u8]`
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/// while the latter is `&[u8; 3]`. That means in general they will have a
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/// different set of methods and different trait implementations.
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///
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/// ```compile_fail
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/// fn f(v: Vec<u8>) {}
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///
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/// f("...".as_bytes().to_owned()); // works
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/// f(b"...".to_owned()); // does not work, because arg is [u8; 3] not Vec<u8>
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///
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/// fn g(r: impl std::io::Read) {}
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///
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/// g("...".as_bytes()); // works
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/// g(b"..."); // does not work
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/// ```
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///
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/// The actual equivalent of `"str".as_bytes()` with the same type is not
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/// `b"str"` but `&b"str"[..]`, which is a great deal of punctuation and not
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/// more readable than a function call.
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///
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/// **Example:**
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/// ```rust
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/// // Bad
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/// let bs = "a byte string".as_bytes();
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///
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/// // Good
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/// let bs = b"a byte string";
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/// ```
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pub STRING_LIT_AS_BYTES,
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nursery,
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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<'tcx> LateLintPass<'tcx> for StringAdd {
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fn check_expr(&mut self, cx: &LateContext<'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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is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(e).peel_refs(), sym::string_type)
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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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declare_clippy_lint! {
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/// **What it does:** Check if the string is transformed to byte array and casted back to string.
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///
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/// **Why is this bad?** It's unnecessary, the string can be used directly.
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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 _ = std::str::from_utf8(&"Hello World!".as_bytes()[6..11]).unwrap();
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/// ```
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/// could be written as
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/// ```rust
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/// let _ = &"Hello World!"[6..11];
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/// ```
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pub STRING_FROM_UTF8_AS_BYTES,
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complexity,
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"casting string slices to byte slices and back"
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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, STRING_FROM_UTF8_AS_BYTES]);
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impl<'tcx> LateLintPass<'tcx> for StringLitAsBytes {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
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use crate::utils::{snippet, snippet_with_applicability};
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use rustc_ast::LitKind;
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if_chain! {
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// Find std::str::converts::from_utf8
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if let Some(args) = match_function_call(cx, e, &paths::STR_FROM_UTF8);
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// Find string::as_bytes
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if let ExprKind::AddrOf(BorrowKind::Ref, _, ref args) = args[0].kind;
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if let ExprKind::Index(ref left, ref right) = args.kind;
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let (method_names, expressions, _) = method_calls(left, 1);
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if method_names.len() == 1;
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if expressions.len() == 1;
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if expressions[0].len() == 1;
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if method_names[0] == sym!(as_bytes);
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// Check for slicer
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if let ExprKind::Struct(QPath::LangItem(LangItem::Range, _), _, _) = right.kind;
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then {
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let mut applicability = Applicability::MachineApplicable;
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let string_expression = &expressions[0][0];
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let snippet_app = snippet_with_applicability(
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cx,
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string_expression.span, "..",
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&mut applicability,
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);
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span_lint_and_sugg(
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cx,
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STRING_FROM_UTF8_AS_BYTES,
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e.span,
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"calling a slice of `as_bytes()` with `from_utf8` should be not necessary",
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"try",
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format!("Some(&{}[{}])", snippet_app, snippet(cx, right.span, "..")),
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applicability
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)
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}
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}
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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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declare_clippy_lint! {
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/// **What it does:** This lint checks for `.to_string()` method calls on values of type `&str`.
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///
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/// **Why is this bad?** The `to_string` method is also used on other types to convert them to a string.
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/// When called on a `&str` it turns the `&str` into the owned variant `String`, which can be better
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/// expressed with `.to_owned()`.
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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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/// // example code where clippy issues a warning
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/// let _ = "str".to_string();
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/// ```
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/// Use instead:
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/// ```rust
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/// // example code which does not raise clippy warning
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/// let _ = "str".to_owned();
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/// ```
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pub STR_TO_STRING,
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restriction,
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"using `to_string()` on a `&str`, which should be `to_owned()`"
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}
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declare_lint_pass!(StrToString => [STR_TO_STRING]);
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impl LateLintPass<'_> for StrToString {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
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if_chain! {
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if let ExprKind::MethodCall(path, _, args, _) = &expr.kind;
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if path.ident.name == sym!(to_string);
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let ty = cx.typeck_results().expr_ty(&args[0]);
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if let ty::Ref(_, ty, ..) = ty.kind();
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if *ty.kind() == ty::Str;
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then {
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span_lint_and_help(
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cx,
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STR_TO_STRING,
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expr.span,
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"`to_string()` called on a `&str`",
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None,
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"consider using `.to_owned()`",
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);
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}
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}
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}
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}
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declare_clippy_lint! {
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/// **What it does:** This lint checks for `.to_string()` method calls on values of type `String`.
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///
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/// **Why is this bad?** The `to_string` method is also used on other types to convert them to a string.
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/// When called on a `String` it only clones the `String`, which can be better expressed with `.clone()`.
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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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/// // example code where clippy issues a warning
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/// let msg = String::from("Hello World");
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/// let _ = msg.to_string();
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/// ```
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/// Use instead:
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/// ```rust
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/// // example code which does not raise clippy warning
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/// let msg = String::from("Hello World");
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/// let _ = msg.clone();
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/// ```
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pub STRING_TO_STRING,
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restriction,
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"using `to_string()` on a `String`, which should be `clone()`"
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}
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declare_lint_pass!(StringToString => [STRING_TO_STRING]);
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impl LateLintPass<'_> for StringToString {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
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if_chain! {
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if let ExprKind::MethodCall(path, _, args, _) = &expr.kind;
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if path.ident.name == sym!(to_string);
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let ty = cx.typeck_results().expr_ty(&args[0]);
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if is_type_diagnostic_item(cx, ty, sym::string_type);
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then {
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span_lint_and_help(
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cx,
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STRING_TO_STRING,
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expr.span,
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"`to_string()` called on a `String`",
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None,
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"consider using `.clone()`",
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);
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}
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}
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}
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}
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