300 lines
10 KiB
Rust
300 lines
10 KiB
Rust
use crate::{map_unit_fn::OPTION_MAP_UNIT_FN, matches::MATCH_AS_REF};
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::higher;
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use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
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use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
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use clippy_utils::{
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can_move_expr_to_closure, in_constant, is_else_clause, is_lang_ctor, is_lint_allowed, path_to_local_id,
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peel_hir_expr_refs,
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};
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use rustc_ast::util::parser::PREC_POSTFIX;
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use rustc_errors::Applicability;
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use rustc_hir::LangItem::{OptionNone, OptionSome};
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use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, HirId, Mutability, Pat, PatKind};
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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_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::{sym, SyntaxContext};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usages of `match` which could be implemented using `map`
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///
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/// ### Why is this bad?
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/// Using the `map` method is clearer and more concise.
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///
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/// ### Example
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/// ```rust
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/// match Some(0) {
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/// Some(x) => Some(x + 1),
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/// None => None,
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/// };
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/// ```
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/// Use instead:
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/// ```rust
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/// Some(0).map(|x| x + 1);
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/// ```
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pub MANUAL_MAP,
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style,
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"reimplementation of `map`"
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}
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declare_lint_pass!(ManualMap => [MANUAL_MAP]);
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impl LateLintPass<'_> for ManualMap {
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#[allow(clippy::too_many_lines)]
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let Some(higher::IfLet {
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let_pat,
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let_expr,
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if_then,
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if_else: Some(if_else),
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}) = higher::IfLet::hir(expr)
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{
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manage_lint(cx, expr, (&let_pat.kind, if_then), (&PatKind::Wild, if_else), let_expr);
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}
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if let ExprKind::Match(scrutinee, [then @ Arm { guard: None, .. }, r#else @ Arm { guard: None, .. }], _) =
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expr.kind
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{
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manage_lint(
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cx,
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expr,
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(&then.pat.kind, then.body),
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(&r#else.pat.kind, r#else.body),
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scrutinee,
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);
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}
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}
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}
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fn manage_lint<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &'tcx Expr<'_>,
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then: (&'tcx PatKind<'_>, &'tcx Expr<'_>),
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r#else: (&'tcx PatKind<'_>, &'tcx Expr<'_>),
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scrut: &'tcx Expr<'_>,
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) {
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if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
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return;
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}
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let (scrutinee_ty, ty_ref_count, ty_mutability) = peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrut));
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if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
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&& is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
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{
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return;
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}
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let (then_pat, then_expr) = then;
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let (else_pat, else_expr) = r#else;
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let expr_ctxt = expr.span.ctxt();
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let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
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try_parse_pattern(cx, then_pat, expr_ctxt),
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try_parse_pattern(cx, else_pat, expr_ctxt),
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) {
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(Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_expr) => {
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(else_expr, pattern, ref_count, true)
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},
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(Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_expr) => {
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(else_expr, pattern, ref_count, false)
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},
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(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_expr) => {
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(then_expr, pattern, ref_count, true)
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},
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(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_expr) => {
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(then_expr, pattern, ref_count, false)
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},
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_ => return,
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};
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// Top level or patterns aren't allowed in closures.
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if matches!(some_pat.kind, PatKind::Or(_)) {
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return;
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}
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let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
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Some(expr) => expr,
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None => return,
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};
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if cx.typeck_results().expr_ty(some_expr) == cx.tcx.types.unit && !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id) {
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return;
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}
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// `map` won't perform any adjustments.
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if !cx.typeck_results().expr_adjustments(some_expr).is_empty() {
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return;
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}
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if !can_move_expr_to_closure(cx, some_expr) {
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return;
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}
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// Determine which binding mode to use.
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let explicit_ref = some_pat.contains_explicit_ref_binding();
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let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
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let as_ref_str = match binding_ref {
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Some(Mutability::Mut) => ".as_mut()",
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Some(Mutability::Not) => ".as_ref()",
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None => "",
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};
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let mut app = Applicability::MachineApplicable;
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// Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
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// it's being passed by value.
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let scrutinee = peel_hir_expr_refs(scrut).0;
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let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
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let scrutinee_str = if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
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format!("({})", scrutinee_str)
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} else {
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scrutinee_str.into()
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};
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let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
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match can_pass_as_func(cx, id, some_expr) {
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Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
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snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
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},
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_ => {
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if path_to_local_id(some_expr, id)
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&& !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
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&& binding_ref.is_some()
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{
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return;
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}
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// `ref` and `ref mut` annotations were handled earlier.
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let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
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"mut "
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} else {
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""
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};
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format!(
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"|{}{}| {}",
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annotation,
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some_binding,
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snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
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)
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},
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}
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} else if !is_wild_none && explicit_ref.is_none() {
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// TODO: handle explicit reference annotations.
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format!(
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"|{}| {}",
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snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0,
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snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
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)
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} else {
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// Refutable bindings and mixed reference annotations can't be handled by `map`.
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return;
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};
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span_lint_and_sugg(
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cx,
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MANUAL_MAP,
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expr.span,
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"manual implementation of `Option::map`",
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"try this",
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if is_else_clause(cx.tcx, expr) {
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format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
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} else {
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format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
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},
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app,
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);
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}
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// Checks whether the expression could be passed as a function, or whether a closure is needed.
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// Returns the function to be passed to `map` if it exists.
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fn can_pass_as_func(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
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match expr.kind {
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ExprKind::Call(func, [arg])
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if path_to_local_id (arg, binding) && cx.typeck_results().expr_adjustments(arg).is_empty() =>
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{
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Some(func)
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},
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_ => None,
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}
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}
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enum OptionPat<'a> {
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Wild,
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None,
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Some {
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// The pattern contained in the `Some` tuple.
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pattern: &'a Pat<'a>,
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// The number of references before the `Some` tuple.
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// e.g. `&&Some(_)` has a ref count of 2.
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ref_count: usize,
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},
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}
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// Try to parse into a recognized `Option` pattern.
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// i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
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fn try_parse_pattern(
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cx: &LateContext<'tcx>,
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pat_kind: &'tcx PatKind<'_>,
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ctxt: SyntaxContext,
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) -> Option<OptionPat<'tcx>> {
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fn f(
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cx: &LateContext<'tcx>,
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pat_kind: &'tcx PatKind<'_>,
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ref_count: usize,
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ctxt: SyntaxContext,
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) -> Option<OptionPat<'tcx>> {
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match pat_kind {
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PatKind::Wild => Some(OptionPat::Wild),
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PatKind::Ref(ref_pat, _) => f(cx, &ref_pat.kind, ref_count + 1, ctxt),
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PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
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PatKind::TupleStruct(ref qpath, [pattern], _) if is_lang_ctor(cx, qpath, OptionSome) => {
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Some(OptionPat::Some { pattern, ref_count })
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},
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_ => None,
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}
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}
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f(cx, pat_kind, 0, ctxt)
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}
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// Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
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fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, ctxt: SyntaxContext) -> Option<&'tcx Expr<'tcx>> {
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// TODO: Allow more complex expressions.
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match expr.kind {
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ExprKind::Call(
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Expr {
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kind: ExprKind::Path(ref qpath),
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..
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},
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[arg],
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) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(arg),
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ExprKind::Block(
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Block {
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stmts: [],
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expr: Some(expr),
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..
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},
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_,
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) => get_some_expr(cx, expr, ctxt),
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_ => None,
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}
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}
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// Checks for the `None` value.
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fn is_none_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
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match expr.kind {
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ExprKind::Path(ref qpath) => is_lang_ctor(cx, qpath, OptionNone),
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ExprKind::Block(
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Block {
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stmts: [],
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expr: Some(expr),
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..
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},
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_,
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) => is_none_expr(cx, expr),
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_ => false,
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}
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}
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