diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/get_first.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/get_first.rs | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/get_first.rs b/src/tools/clippy/clippy_lints/src/get_first.rs new file mode 100644 index 000000000..529f7baba --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/get_first.rs @@ -0,0 +1,68 @@ +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::source::snippet_with_applicability; +use clippy_utils::{is_slice_of_primitives, match_def_path, paths}; +use if_chain::if_chain; +use rustc_ast::LitKind; +use rustc_errors::Applicability; +use rustc_hir as hir; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::source_map::Spanned; + +declare_clippy_lint! { + /// ### What it does + /// Checks for using `x.get(0)` instead of + /// `x.first()`. + /// + /// ### Why is this bad? + /// Using `x.first()` is easier to read and has the same + /// result. + /// + /// ### Example + /// ```rust + /// let x = vec![2, 3, 5]; + /// let first_element = x.get(0); + /// ``` + /// + /// Use instead: + /// ```rust + /// let x = vec![2, 3, 5]; + /// let first_element = x.first(); + /// ``` + #[clippy::version = "1.63.0"] + pub GET_FIRST, + style, + "Using `x.get(0)` when `x.first()` is simpler" +} +declare_lint_pass!(GetFirst => [GET_FIRST]); + +impl<'tcx> LateLintPass<'tcx> for GetFirst { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { + if_chain! { + if let hir::ExprKind::MethodCall(_, [struct_calling_on, method_arg], _) = &expr.kind; + if let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id); + if match_def_path(cx, expr_def_id, &paths::SLICE_GET); + + if let Some(_) = is_slice_of_primitives(cx, struct_calling_on); + if let hir::ExprKind::Lit(Spanned { node: LitKind::Int(0, _), .. }) = method_arg.kind; + + then { + let mut applicability = Applicability::MachineApplicable; + let slice_name = snippet_with_applicability( + cx, + struct_calling_on.span, "..", + &mut applicability, + ); + span_lint_and_sugg( + cx, + GET_FIRST, + expr.span, + &format!("accessing first element with `{0}.get(0)`", slice_name), + "try", + format!("{}.first()", slice_name), + applicability, + ); + } + } + } +} |