--- /dev/null
+use crate::{
+ map_unit_fn::OPTION_MAP_UNIT_FN,
+ matches::MATCH_AS_REF,
+ utils::{
+ can_partially_move_ty, is_allowed, is_type_diagnostic_item, match_def_path, match_var, paths,
+ peel_hir_expr_refs, peel_mid_ty_refs_is_mutable, snippet_with_applicability, snippet_with_context,
+ span_lint_and_sugg,
+ },
+};
+use rustc_ast::util::parser::PREC_POSTFIX;
+use rustc_errors::Applicability;
+use rustc_hir::{
+ def::Res,
+ intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
+ Arm, BindingAnnotation, Block, Expr, ExprKind, Mutability, Pat, PatKind, Path, QPath,
+};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{
+ symbol::{sym, Ident},
+ SyntaxContext,
+};
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for usages of `match` which could be implemented using `map`
+ ///
+ /// **Why is this bad?** Using the `map` method is clearer and more concise.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// match Some(0) {
+ /// Some(x) => Some(x + 1),
+ /// None => None,
+ /// };
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// Some(0).map(|x| x + 1);
+ /// ```
+ pub MANUAL_MAP,
+ style,
+ "reimplementation of `map`"
+}
+
+declare_lint_pass!(ManualMap => [MANUAL_MAP]);
+
+impl LateLintPass<'_> for ManualMap {
+ #[allow(clippy::too_many_lines)]
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if in_external_macro(cx.sess(), expr.span) {
+ return;
+ }
+
+ if let ExprKind::Match(scrutinee, [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }], _) =
+ expr.kind
+ {
+ let (scrutinee_ty, ty_ref_count, ty_mutability) =
+ peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
+ if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
+ && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
+ {
+ return;
+ }
+
+ let expr_ctxt = expr.span.ctxt();
+ let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
+ try_parse_pattern(cx, arm1.pat, expr_ctxt),
+ try_parse_pattern(cx, arm2.pat, expr_ctxt),
+ ) {
+ (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count }))
+ if is_none_expr(cx, arm1.body) =>
+ {
+ (arm2.body, pattern, ref_count, true)
+ },
+ (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count }))
+ if is_none_expr(cx, arm1.body) =>
+ {
+ (arm2.body, pattern, ref_count, false)
+ },
+ (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild))
+ if is_none_expr(cx, arm2.body) =>
+ {
+ (arm1.body, pattern, ref_count, true)
+ },
+ (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None))
+ if is_none_expr(cx, arm2.body) =>
+ {
+ (arm1.body, pattern, ref_count, false)
+ },
+ _ => return,
+ };
+
+ // Top level or patterns aren't allowed in closures.
+ if matches!(some_pat.kind, PatKind::Or(_)) {
+ return;
+ }
+
+ let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
+ Some(expr) => expr,
+ None => return,
+ };
+
+ if cx.typeck_results().expr_ty(some_expr) == cx.tcx.types.unit
+ && !is_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
+ {
+ return;
+ }
+
+ if !can_move_expr_to_closure(cx, some_expr) {
+ return;
+ }
+
+ // Determine which binding mode to use.
+ let explicit_ref = some_pat.contains_explicit_ref_binding();
+ let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
+
+ let as_ref_str = match binding_ref {
+ Some(Mutability::Mut) => ".as_mut()",
+ Some(Mutability::Not) => ".as_ref()",
+ None => "",
+ };
+
+ let mut app = Applicability::MachineApplicable;
+
+ // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
+ // it's being passed by value.
+ let scrutinee = peel_hir_expr_refs(scrutinee).0;
+ let scrutinee_str = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
+ let scrutinee_str =
+ if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
+ format!("({})", scrutinee_str)
+ } else {
+ scrutinee_str.into()
+ };
+
+ let body_str = if let PatKind::Binding(annotation, _, some_binding, None) = some_pat.kind {
+ match can_pass_as_func(cx, some_binding, some_expr) {
+ Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
+ snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
+ },
+ _ => {
+ if match_var(some_expr, some_binding.name)
+ && !is_allowed(cx, MATCH_AS_REF, expr.hir_id)
+ && binding_ref.is_some()
+ {
+ return;
+ }
+
+ // `ref` and `ref mut` annotations were handled earlier.
+ let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
+ "mut "
+ } else {
+ ""
+ };
+ format!(
+ "|{}{}| {}",
+ annotation,
+ some_binding,
+ snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app)
+ )
+ },
+ }
+ } else if !is_wild_none && explicit_ref.is_none() {
+ // TODO: handle explicit reference annotations.
+ format!(
+ "|{}| {}",
+ snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app),
+ snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app)
+ )
+ } else {
+ // Refutable bindings and mixed reference annotations can't be handled by `map`.
+ return;
+ };
+
+ span_lint_and_sugg(
+ cx,
+ MANUAL_MAP,
+ expr.span,
+ "manual implementation of `Option::map`",
+ "try this",
+ format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str),
+ app,
+ );
+ }
+ }
+}
+
+// Checks if the expression can be moved into a closure as is.
+fn can_move_expr_to_closure(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
+ struct V<'cx, 'tcx> {
+ cx: &'cx LateContext<'tcx>,
+ make_closure: bool,
+ }
+ impl Visitor<'tcx> for V<'_, 'tcx> {
+ type Map = ErasedMap<'tcx>;
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::None
+ }
+
+ fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
+ match e.kind {
+ ExprKind::Break(..)
+ | ExprKind::Continue(_)
+ | ExprKind::Ret(_)
+ | ExprKind::Yield(..)
+ | ExprKind::InlineAsm(_)
+ | ExprKind::LlvmInlineAsm(_) => {
+ self.make_closure = false;
+ },
+ // Accessing a field of a local value can only be done if the type isn't
+ // partially moved.
+ ExprKind::Field(base_expr, _)
+ if matches!(
+ base_expr.kind,
+ ExprKind::Path(QPath::Resolved(_, Path { res: Res::Local(_), .. }))
+ ) && can_partially_move_ty(self.cx, self.cx.typeck_results().expr_ty(base_expr)) =>
+ {
+ // TODO: check if the local has been partially moved. Assume it has for now.
+ self.make_closure = false;
+ return;
+ }
+ _ => (),
+ };
+ walk_expr(self, e);
+ }
+ }
+
+ let mut v = V { cx, make_closure: true };
+ v.visit_expr(expr);
+ v.make_closure
+}
+
+// Checks whether the expression could be passed as a function, or whether a closure is needed.
+// Returns the function to be passed to `map` if it exists.
+fn can_pass_as_func(cx: &LateContext<'tcx>, binding: Ident, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
+ match expr.kind {
+ ExprKind::Call(func, [arg])
+ if match_var(arg, binding.name) && cx.typeck_results().expr_adjustments(arg).is_empty() =>
+ {
+ Some(func)
+ },
+ _ => None,
+ }
+}
+
+enum OptionPat<'a> {
+ Wild,
+ None,
+ Some {
+ // The pattern contained in the `Some` tuple.
+ pattern: &'a Pat<'a>,
+ // The number of references before the `Some` tuple.
+ // e.g. `&&Some(_)` has a ref count of 2.
+ ref_count: usize,
+ },
+}
+
+// Try to parse into a recognized `Option` pattern.
+// i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
+fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
+ fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
+ match pat.kind {
+ PatKind::Wild => Some(OptionPat::Wild),
+ PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
+ PatKind::Path(QPath::Resolved(None, path))
+ if path
+ .res
+ .opt_def_id()
+ .map_or(false, |id| match_def_path(cx, id, &paths::OPTION_NONE)) =>
+ {
+ Some(OptionPat::None)
+ },
+ PatKind::TupleStruct(QPath::Resolved(None, path), [pattern], _)
+ if path
+ .res
+ .opt_def_id()
+ .map_or(false, |id| match_def_path(cx, id, &paths::OPTION_SOME))
+ && pat.span.ctxt() == ctxt =>
+ {
+ Some(OptionPat::Some { pattern, ref_count })
+ },
+ _ => None,
+ }
+ }
+ f(cx, pat, 0, ctxt)
+}
+
+// Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
+fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, ctxt: SyntaxContext) -> Option<&'tcx Expr<'tcx>> {
+ // TODO: Allow more complex expressions.
+ match expr.kind {
+ ExprKind::Call(
+ Expr {
+ kind: ExprKind::Path(QPath::Resolved(None, path)),
+ ..
+ },
+ [arg],
+ ) if ctxt == expr.span.ctxt() => {
+ if match_def_path(cx, path.res.opt_def_id()?, &paths::OPTION_SOME) {
+ Some(arg)
+ } else {
+ None
+ }
+ },
+ ExprKind::Block(
+ Block {
+ stmts: [],
+ expr: Some(expr),
+ ..
+ },
+ _,
+ ) => get_some_expr(cx, expr, ctxt),
+ _ => None,
+ }
+}
+
+// Checks for the `None` value.
+fn is_none_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
+ match expr.kind {
+ ExprKind::Path(QPath::Resolved(None, path)) => path
+ .res
+ .opt_def_id()
+ .map_or(false, |id| match_def_path(cx, id, &paths::OPTION_NONE)),
+ ExprKind::Block(
+ Block {
+ stmts: [],
+ expr: Some(expr),
+ ..
+ },
+ _,
+ ) => is_none_expr(cx, expr),
+ _ => false,
+ }
+}
projects / rustc.git / blobdiff