75 lines
2.9 KiB
Rust
75 lines
2.9 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::ty::is_type_lang_item;
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use rustc_ast::ast::LitKind;
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use rustc_errors::Applicability;
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use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty;
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use rustc_session::declare_lint_pass;
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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///
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/// Detects cases of owned empty strings being passed as an argument to a function expecting `&str`
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///
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/// ### Why is this bad?
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///
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/// This results in longer and less readable code
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///
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/// ### Example
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/// ```no_run
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/// vec!["1", "2", "3"].join(&String::new());
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/// ```
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/// Use instead:
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/// ```no_run
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/// vec!["1", "2", "3"].join("");
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/// ```
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#[clippy::version = "1.62.0"]
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pub UNNECESSARY_OWNED_EMPTY_STRINGS,
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style,
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"detects cases of references to owned empty strings being passed as an argument to a function expecting `&str`"
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}
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declare_lint_pass!(UnnecessaryOwnedEmptyStrings => [UNNECESSARY_OWNED_EMPTY_STRINGS]);
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impl<'tcx> LateLintPass<'tcx> for UnnecessaryOwnedEmptyStrings {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner_expr) = expr.kind
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&& let ExprKind::Call(fun, args) = inner_expr.kind
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&& let ExprKind::Path(ref qpath) = fun.kind
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&& let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id()
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&& let ty::Ref(_, inner_str, _) = cx.typeck_results().expr_ty_adjusted(expr).kind()
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&& inner_str.is_str()
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{
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if cx.tcx.is_diagnostic_item(sym::string_new, fun_def_id) {
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span_lint_and_sugg(
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cx,
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UNNECESSARY_OWNED_EMPTY_STRINGS,
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expr.span,
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"usage of `&String::new()` for a function expecting a `&str` argument",
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"try",
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"\"\"".to_owned(),
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Applicability::MachineApplicable,
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);
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} else if cx.tcx.is_diagnostic_item(sym::from_fn, fun_def_id)
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&& let [.., last_arg] = args
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&& let ExprKind::Lit(spanned) = &last_arg.kind
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&& let LitKind::Str(symbol, _) = spanned.node
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&& symbol.is_empty()
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&& let inner_expr_type = cx.typeck_results().expr_ty(inner_expr)
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&& is_type_lang_item(cx, inner_expr_type, LangItem::String)
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{
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span_lint_and_sugg(
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cx,
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UNNECESSARY_OWNED_EMPTY_STRINGS,
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expr.span,
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"usage of `&String::from(\"\")` for a function expecting a `&str` argument",
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"try",
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"\"\"".to_owned(),
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Applicability::MachineApplicable,
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);
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}
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}
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}
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}
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