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