diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/unnecessary_owned_empty_strings.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/unnecessary_owned_empty_strings.rs | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/unnecessary_owned_empty_strings.rs b/src/tools/clippy/clippy_lints/src/unnecessary_owned_empty_strings.rs new file mode 100644 index 000000000..8a4f4c0ad --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/unnecessary_owned_empty_strings.rs @@ -0,0 +1,81 @@ +use clippy_utils::{diagnostics::span_lint_and_sugg, ty::is_type_diagnostic_item}; +use clippy_utils::{match_def_path, paths}; +use if_chain::if_chain; +use rustc_ast::ast::LitKind; +use rustc_errors::Applicability; +use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::sym; + +declare_clippy_lint! { + /// ### What it does + /// + /// Detects cases of owned empty strings being passed as an argument to a function expecting `&str` + /// + /// ### Why is this bad? + /// + /// This results in longer and less readable code + /// + /// ### Example + /// ```rust + /// vec!["1", "2", "3"].join(&String::new()); + /// ``` + /// Use instead: + /// ```rust + /// vec!["1", "2", "3"].join(""); + /// ``` + #[clippy::version = "1.62.0"] + pub UNNECESSARY_OWNED_EMPTY_STRINGS, + style, + "detects cases of references to owned empty strings being passed as an argument to a function expecting `&str`" +} +declare_lint_pass!(UnnecessaryOwnedEmptyStrings => [UNNECESSARY_OWNED_EMPTY_STRINGS]); + +impl<'tcx> LateLintPass<'tcx> for UnnecessaryOwnedEmptyStrings { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { + if_chain! { + if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner_expr) = expr.kind; + if let ExprKind::Call(fun, args) = inner_expr.kind; + if let ExprKind::Path(ref qpath) = fun.kind; + if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id(); + if let ty::Ref(_, inner_str, _) = cx.typeck_results().expr_ty_adjusted(expr).kind(); + if inner_str.is_str(); + then { + if match_def_path(cx, fun_def_id, &paths::STRING_NEW) { + span_lint_and_sugg( + cx, + UNNECESSARY_OWNED_EMPTY_STRINGS, + expr.span, + "usage of `&String::new()` for a function expecting a `&str` argument", + "try", + "\"\"".to_owned(), + Applicability::MachineApplicable, + ); + } else { + if_chain! { + if match_def_path(cx, fun_def_id, &paths::FROM_FROM); + if let [.., last_arg] = args; + if let ExprKind::Lit(spanned) = &last_arg.kind; + if let LitKind::Str(symbol, _) = spanned.node; + if symbol.is_empty(); + let inner_expr_type = cx.typeck_results().expr_ty(inner_expr); + if is_type_diagnostic_item(cx, inner_expr_type, sym::String); + then { + span_lint_and_sugg( + cx, + UNNECESSARY_OWNED_EMPTY_STRINGS, + expr.span, + "usage of `&String::from(\"\")` for a function expecting a `&str` argument", + "try", + "\"\"".to_owned(), + Applicability::MachineApplicable, + ); + } + } + } + } + } + } +} |