335 lines
12 KiB
Rust
335 lines
12 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::source::{snippet_with_applicability, snippet_with_context};
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use clippy_utils::ty::{can_partially_move_ty, is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
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use clippy_utils::{is_allowed, match_def_path, match_var, paths, peel_hir_expr_refs};
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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::{
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def::Res,
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intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
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Arm, BindingAnnotation, Block, Expr, ExprKind, Mutability, Pat, PatKind, Path, QPath,
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};
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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::{
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symbol::{sym, Ident},
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SyntaxContext,
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};
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declare_clippy_lint! {
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/// **What it does:** Checks for usages of `match` which could be implemented using `map`
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///
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/// **Why is this bad?** Using the `map` method is clearer and more concise.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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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 in_external_macro(cx.sess(), expr.span) {
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return;
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}
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if let ExprKind::Match(scrutinee, [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }], _) =
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expr.kind
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{
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let (scrutinee_ty, ty_ref_count, ty_mutability) =
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peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
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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 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, arm1.pat, expr_ctxt),
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try_parse_pattern(cx, arm2.pat, expr_ctxt),
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) {
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(Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count }))
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if is_none_expr(cx, arm1.body) =>
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{
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(arm2.body, pattern, ref_count, true)
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},
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(Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count }))
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if is_none_expr(cx, arm1.body) =>
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{
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(arm2.body, pattern, ref_count, false)
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},
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(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild))
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if is_none_expr(cx, arm2.body) =>
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{
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(arm1.body, pattern, ref_count, true)
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},
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(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None))
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if is_none_expr(cx, arm2.body) =>
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{
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(arm1.body, 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
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&& !is_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
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{
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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(scrutinee).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 =
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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, _, some_binding, None) = some_pat.kind {
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match can_pass_as_func(cx, some_binding, 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 match_var(some_expr, some_binding.name)
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&& !is_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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format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str),
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app,
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);
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}
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}
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}
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// Checks if the expression can be moved into a closure as is.
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fn can_move_expr_to_closure(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
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struct V<'cx, 'tcx> {
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cx: &'cx LateContext<'tcx>,
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make_closure: bool,
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}
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impl Visitor<'tcx> for V<'_, 'tcx> {
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type Map = ErasedMap<'tcx>;
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::None
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}
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fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
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match e.kind {
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ExprKind::Break(..)
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| ExprKind::Continue(_)
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| ExprKind::Ret(_)
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| ExprKind::Yield(..)
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| ExprKind::InlineAsm(_)
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| ExprKind::LlvmInlineAsm(_) => {
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self.make_closure = false;
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},
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// Accessing a field of a local value can only be done if the type isn't
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// partially moved.
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ExprKind::Field(base_expr, _)
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if matches!(
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base_expr.kind,
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ExprKind::Path(QPath::Resolved(_, Path { res: Res::Local(_), .. }))
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) && can_partially_move_ty(self.cx, self.cx.typeck_results().expr_ty(base_expr)) =>
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{
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// TODO: check if the local has been partially moved. Assume it has for now.
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self.make_closure = false;
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return;
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}
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_ => (),
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};
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walk_expr(self, e);
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}
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}
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let mut v = V { cx, make_closure: true };
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v.visit_expr(expr);
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v.make_closure
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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: Ident, 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 match_var(arg, binding.name) && 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(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
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fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> 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(pat, _) => f(cx, pat, ref_count + 1, ctxt),
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PatKind::Path(QPath::Resolved(None, path))
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if path
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.res
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.opt_def_id()
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.map_or(false, |id| match_def_path(cx, id, &paths::OPTION_NONE)) =>
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{
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Some(OptionPat::None)
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},
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PatKind::TupleStruct(QPath::Resolved(None, path), [pattern], _)
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if path
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.res
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.opt_def_id()
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.map_or(false, |id| match_def_path(cx, id, &paths::OPTION_SOME))
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&& pat.span.ctxt() == ctxt =>
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{
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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, 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(QPath::Resolved(None, path)),
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..
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},
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[arg],
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) if ctxt == expr.span.ctxt() => {
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if match_def_path(cx, path.res.opt_def_id()?, &paths::OPTION_SOME) {
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Some(arg)
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} else {
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None
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}
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},
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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(QPath::Resolved(None, path)) => path
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.res
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.opt_def_id()
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.map_or(false, |id| match_def_path(cx, id, &paths::OPTION_NONE)),
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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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