646 lines
25 KiB
Rust
646 lines
25 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::{reindent_multiline, snippet_indent, snippet_with_applicability, snippet_with_context};
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use clippy_utils::{
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can_move_expr_to_closure_no_visit, higher, is_expr_final_block_expr, is_expr_used_or_unified, match_def_path,
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paths, peel_hir_expr_while, SpanlessEq,
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};
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use core::fmt::{self, Write};
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use rustc_errors::Applicability;
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use rustc_hir::hir_id::HirIdSet;
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use rustc_hir::intravisit::{walk_expr, Visitor};
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use rustc_hir::{Block, Expr, ExprKind, Guard, HirId, Let, Pat, Stmt, StmtKind, UnOp};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::{Span, SyntaxContext, DUMMY_SP};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `contains_key` + `insert` on `HashMap`
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/// or `BTreeMap`.
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///
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/// ### Why is this bad?
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/// Using `entry` is more efficient.
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///
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/// ### Known problems
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/// The suggestion may have type inference errors in some cases. e.g.
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/// ```no_run
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/// let mut map = std::collections::HashMap::new();
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/// let _ = if !map.contains_key(&0) {
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/// map.insert(0, 0)
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/// } else {
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/// None
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/// };
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/// ```
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///
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/// ### Example
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/// ```no_run
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/// # use std::collections::HashMap;
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/// # let mut map = HashMap::new();
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/// # let k = 1;
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/// # let v = 1;
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/// if !map.contains_key(&k) {
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/// map.insert(k, v);
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/// }
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/// ```
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/// Use instead:
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/// ```no_run
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/// # use std::collections::HashMap;
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/// # let mut map = HashMap::new();
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/// # let k = 1;
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/// # let v = 1;
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/// map.entry(k).or_insert(v);
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub MAP_ENTRY,
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perf,
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"use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
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}
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declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
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impl<'tcx> LateLintPass<'tcx> for HashMapPass {
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#[expect(clippy::too_many_lines)]
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if expr.span.from_expansion() {
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return;
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}
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let Some(higher::If {
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cond: cond_expr,
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then: then_expr,
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r#else: else_expr,
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}) = higher::If::hir(expr)
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else {
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return;
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};
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let Some((map_ty, contains_expr)) = try_parse_contains(cx, cond_expr) else {
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return;
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};
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let Some(then_search) = find_insert_calls(cx, &contains_expr, then_expr) else {
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return;
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};
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let mut app = Applicability::MachineApplicable;
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let map_str = snippet_with_context(cx, contains_expr.map.span, contains_expr.call_ctxt, "..", &mut app).0;
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let key_str = snippet_with_context(cx, contains_expr.key.span, contains_expr.call_ctxt, "..", &mut app).0;
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let sugg = if let Some(else_expr) = else_expr {
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let Some(else_search) = find_insert_calls(cx, &contains_expr, else_expr) else {
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return;
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};
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if then_search.edits.is_empty() && else_search.edits.is_empty() {
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// No insertions
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return;
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} else if then_search.edits.is_empty() || else_search.edits.is_empty() {
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// if .. { insert } else { .. } or if .. { .. } else { insert }
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let ((then_str, entry_kind), else_str) = match (else_search.edits.is_empty(), contains_expr.negated) {
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(true, true) => (
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then_search.snippet_vacant(cx, then_expr.span, &mut app),
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snippet_with_applicability(cx, else_expr.span, "{ .. }", &mut app),
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),
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(true, false) => (
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then_search.snippet_occupied(cx, then_expr.span, &mut app),
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snippet_with_applicability(cx, else_expr.span, "{ .. }", &mut app),
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),
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(false, true) => (
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else_search.snippet_occupied(cx, else_expr.span, &mut app),
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snippet_with_applicability(cx, then_expr.span, "{ .. }", &mut app),
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),
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(false, false) => (
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else_search.snippet_vacant(cx, else_expr.span, &mut app),
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snippet_with_applicability(cx, then_expr.span, "{ .. }", &mut app),
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),
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};
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format!(
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"if let {}::{entry_kind} = {map_str}.entry({key_str}) {then_str} else {else_str}",
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map_ty.entry_path(),
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)
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} else {
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// if .. { insert } else { insert }
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let ((then_str, then_entry), (else_str, else_entry)) = if contains_expr.negated {
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(
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then_search.snippet_vacant(cx, then_expr.span, &mut app),
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else_search.snippet_occupied(cx, else_expr.span, &mut app),
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)
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} else {
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(
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then_search.snippet_occupied(cx, then_expr.span, &mut app),
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else_search.snippet_vacant(cx, else_expr.span, &mut app),
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)
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};
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let indent_str = snippet_indent(cx, expr.span);
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let indent_str = indent_str.as_deref().unwrap_or("");
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format!(
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"match {map_str}.entry({key_str}) {{\n{indent_str} {entry}::{then_entry} => {}\n\
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{indent_str} {entry}::{else_entry} => {}\n{indent_str}}}",
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reindent_multiline(then_str.into(), true, Some(4 + indent_str.len())),
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reindent_multiline(else_str.into(), true, Some(4 + indent_str.len())),
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entry = map_ty.entry_path(),
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)
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}
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} else {
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if then_search.edits.is_empty() {
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// no insertions
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return;
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}
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// if .. { insert }
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if !then_search.allow_insert_closure {
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let (body_str, entry_kind) = if contains_expr.negated {
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then_search.snippet_vacant(cx, then_expr.span, &mut app)
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} else {
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then_search.snippet_occupied(cx, then_expr.span, &mut app)
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};
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format!(
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"if let {}::{entry_kind} = {map_str}.entry({key_str}) {body_str}",
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map_ty.entry_path(),
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)
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} else if let Some(insertion) = then_search.as_single_insertion() {
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let value_str = snippet_with_context(cx, insertion.value.span, then_expr.span.ctxt(), "..", &mut app).0;
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if contains_expr.negated {
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if insertion.value.can_have_side_effects() {
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format!("{map_str}.entry({key_str}).or_insert_with(|| {value_str});")
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} else {
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format!("{map_str}.entry({key_str}).or_insert({value_str});")
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}
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} else {
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// TODO: suggest using `if let Some(v) = map.get_mut(k) { .. }` here.
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// This would need to be a different lint.
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return;
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}
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} else {
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let block_str = then_search.snippet_closure(cx, then_expr.span, &mut app);
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if contains_expr.negated {
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format!("{map_str}.entry({key_str}).or_insert_with(|| {block_str});")
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} else {
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// TODO: suggest using `if let Some(v) = map.get_mut(k) { .. }` here.
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// This would need to be a different lint.
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return;
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}
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}
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};
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span_lint_and_sugg(
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cx,
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MAP_ENTRY,
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expr.span,
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&format!("usage of `contains_key` followed by `insert` on a `{}`", map_ty.name()),
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"try",
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sugg,
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app,
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);
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}
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}
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#[derive(Clone, Copy)]
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enum MapType {
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Hash,
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BTree,
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}
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impl MapType {
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fn name(self) -> &'static str {
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match self {
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Self::Hash => "HashMap",
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Self::BTree => "BTreeMap",
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}
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}
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fn entry_path(self) -> &'static str {
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match self {
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Self::Hash => "std::collections::hash_map::Entry",
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Self::BTree => "std::collections::btree_map::Entry",
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}
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}
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}
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struct ContainsExpr<'tcx> {
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negated: bool,
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map: &'tcx Expr<'tcx>,
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key: &'tcx Expr<'tcx>,
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call_ctxt: SyntaxContext,
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}
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fn try_parse_contains<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> Option<(MapType, ContainsExpr<'tcx>)> {
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let mut negated = false;
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let expr = peel_hir_expr_while(expr, |e| match e.kind {
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ExprKind::Unary(UnOp::Not, e) => {
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negated = !negated;
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Some(e)
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},
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_ => None,
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});
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match expr.kind {
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ExprKind::MethodCall(
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_,
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map,
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[
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Expr {
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kind: ExprKind::AddrOf(_, _, key),
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span: key_span,
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..
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},
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],
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_,
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) if key_span.eq_ctxt(expr.span) => {
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let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
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let expr = ContainsExpr {
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negated,
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map,
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key,
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call_ctxt: expr.span.ctxt(),
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};
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if match_def_path(cx, id, &paths::BTREEMAP_CONTAINS_KEY) {
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Some((MapType::BTree, expr))
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} else if match_def_path(cx, id, &paths::HASHMAP_CONTAINS_KEY) {
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Some((MapType::Hash, expr))
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} else {
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None
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}
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},
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_ => None,
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}
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}
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struct InsertExpr<'tcx> {
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map: &'tcx Expr<'tcx>,
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key: &'tcx Expr<'tcx>,
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value: &'tcx Expr<'tcx>,
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}
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fn try_parse_insert<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<InsertExpr<'tcx>> {
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if let ExprKind::MethodCall(_, map, [key, value], _) = expr.kind {
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let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
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if match_def_path(cx, id, &paths::BTREEMAP_INSERT) || match_def_path(cx, id, &paths::HASHMAP_INSERT) {
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Some(InsertExpr { map, key, value })
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} else {
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None
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}
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} else {
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None
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}
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}
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/// An edit that will need to be made to move the expression to use the entry api
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#[derive(Clone, Copy)]
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enum Edit<'tcx> {
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/// A semicolon that needs to be removed. Used to create a closure for `insert_with`.
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RemoveSemi(Span),
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/// An insertion into the map.
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Insertion(Insertion<'tcx>),
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}
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impl<'tcx> Edit<'tcx> {
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fn as_insertion(self) -> Option<Insertion<'tcx>> {
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if let Self::Insertion(i) = self { Some(i) } else { None }
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}
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}
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#[derive(Clone, Copy)]
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struct Insertion<'tcx> {
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call: &'tcx Expr<'tcx>,
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value: &'tcx Expr<'tcx>,
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}
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/// This visitor needs to do a multiple things:
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/// * Find all usages of the map. An insertion can only be made before any other usages of the map.
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/// * Determine if there's an insertion using the same key. There's no need for the entry api
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/// otherwise.
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/// * Determine if the final statement executed is an insertion. This is needed to use
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/// `or_insert_with`.
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/// * Determine if there's any sub-expression that can't be placed in a closure.
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/// * Determine if there's only a single insert statement. `or_insert` can be used in this case.
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#[expect(clippy::struct_excessive_bools)]
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struct InsertSearcher<'cx, 'tcx> {
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cx: &'cx LateContext<'tcx>,
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/// The map expression used in the contains call.
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map: &'tcx Expr<'tcx>,
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/// The key expression used in the contains call.
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key: &'tcx Expr<'tcx>,
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/// The context of the top level block. All insert calls must be in the same context.
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ctxt: SyntaxContext,
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/// Whether this expression can be safely moved into a closure.
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allow_insert_closure: bool,
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/// Whether this expression can use the entry api.
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can_use_entry: bool,
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/// Whether this expression is the final expression in this code path. This may be a statement.
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in_tail_pos: bool,
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// Is this expression a single insert. A slightly better suggestion can be made in this case.
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is_single_insert: bool,
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/// If the visitor has seen the map being used.
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is_map_used: bool,
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/// The locations where changes need to be made for the suggestion.
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edits: Vec<Edit<'tcx>>,
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/// A stack of loops the visitor is currently in.
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loops: Vec<HirId>,
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/// Local variables created in the expression. These don't need to be captured.
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locals: HirIdSet,
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}
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impl<'tcx> InsertSearcher<'_, 'tcx> {
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/// Visit the expression as a branch in control flow. Multiple insert calls can be used, but
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/// only if they are on separate code paths. This will return whether the map was used in the
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/// given expression.
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fn visit_cond_arm(&mut self, e: &'tcx Expr<'_>) -> bool {
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let is_map_used = self.is_map_used;
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let in_tail_pos = self.in_tail_pos;
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self.visit_expr(e);
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let res = self.is_map_used;
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self.is_map_used = is_map_used;
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self.in_tail_pos = in_tail_pos;
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res
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}
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/// Visits an expression which is not itself in a tail position, but other sibling expressions
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/// may be. e.g. if conditions
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fn visit_non_tail_expr(&mut self, e: &'tcx Expr<'_>) {
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let in_tail_pos = self.in_tail_pos;
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self.in_tail_pos = false;
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self.visit_expr(e);
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self.in_tail_pos = in_tail_pos;
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}
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}
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impl<'tcx> Visitor<'tcx> for InsertSearcher<'_, 'tcx> {
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fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
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match stmt.kind {
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StmtKind::Semi(e) => {
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self.visit_expr(e);
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if self.in_tail_pos && self.allow_insert_closure {
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// The spans are used to slice the top level expression into multiple parts. This requires that
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// they all come from the same part of the source code.
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if stmt.span.ctxt() == self.ctxt && e.span.ctxt() == self.ctxt {
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self.edits
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.push(Edit::RemoveSemi(stmt.span.trim_start(e.span).unwrap_or(DUMMY_SP)));
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} else {
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self.allow_insert_closure = false;
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}
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}
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},
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StmtKind::Expr(e) => self.visit_expr(e),
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StmtKind::Local(l) => {
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self.visit_pat(l.pat);
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if let Some(e) = l.init {
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self.allow_insert_closure &= !self.in_tail_pos;
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self.in_tail_pos = false;
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self.is_single_insert = false;
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self.visit_expr(e);
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}
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},
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StmtKind::Item(_) => {
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self.allow_insert_closure &= !self.in_tail_pos;
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self.is_single_insert = false;
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},
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}
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}
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fn visit_block(&mut self, block: &'tcx Block<'_>) {
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// If the block is in a tail position, then the last expression (possibly a statement) is in the
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// tail position. The rest, however, are not.
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match (block.stmts, block.expr) {
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([], None) => {
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self.allow_insert_closure &= !self.in_tail_pos;
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},
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([], Some(expr)) => self.visit_expr(expr),
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(stmts, Some(expr)) => {
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let in_tail_pos = self.in_tail_pos;
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self.in_tail_pos = false;
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for stmt in stmts {
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self.visit_stmt(stmt);
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}
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self.in_tail_pos = in_tail_pos;
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self.visit_expr(expr);
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},
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([stmts @ .., stmt], None) => {
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let in_tail_pos = self.in_tail_pos;
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self.in_tail_pos = false;
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for stmt in stmts {
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self.visit_stmt(stmt);
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}
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self.in_tail_pos = in_tail_pos;
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self.visit_stmt(stmt);
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},
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}
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}
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fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
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if !self.can_use_entry {
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return;
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}
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match try_parse_insert(self.cx, expr) {
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Some(insert_expr) if SpanlessEq::new(self.cx).eq_expr(self.map, insert_expr.map) => {
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// Multiple inserts, inserts with a different key, and inserts from a macro can't use the entry api.
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if self.is_map_used
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|| !SpanlessEq::new(self.cx).eq_expr(self.key, insert_expr.key)
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|| expr.span.ctxt() != self.ctxt
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{
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self.can_use_entry = false;
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return;
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}
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self.edits.push(Edit::Insertion(Insertion {
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call: expr,
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value: insert_expr.value,
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}));
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self.is_map_used = true;
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self.allow_insert_closure &= self.in_tail_pos;
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// The value doesn't affect whether there is only a single insert expression.
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let is_single_insert = self.is_single_insert;
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self.visit_non_tail_expr(insert_expr.value);
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self.is_single_insert = is_single_insert;
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},
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_ if SpanlessEq::new(self.cx).eq_expr(self.map, expr) => {
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self.is_map_used = true;
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},
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_ => match expr.kind {
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ExprKind::If(cond_expr, then_expr, Some(else_expr)) => {
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self.is_single_insert = false;
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self.visit_non_tail_expr(cond_expr);
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|
// Each branch may contain it's own insert expression.
|
|
let mut is_map_used = self.visit_cond_arm(then_expr);
|
|
is_map_used |= self.visit_cond_arm(else_expr);
|
|
self.is_map_used = is_map_used;
|
|
},
|
|
ExprKind::Match(scrutinee_expr, arms, _) => {
|
|
self.is_single_insert = false;
|
|
self.visit_non_tail_expr(scrutinee_expr);
|
|
// Each branch may contain it's own insert expression.
|
|
let mut is_map_used = self.is_map_used;
|
|
for arm in arms {
|
|
self.visit_pat(arm.pat);
|
|
if let Some(Guard::If(guard) | Guard::IfLet(&Let { init: guard, .. })) = arm.guard {
|
|
self.visit_non_tail_expr(guard);
|
|
}
|
|
is_map_used |= self.visit_cond_arm(arm.body);
|
|
}
|
|
self.is_map_used = is_map_used;
|
|
},
|
|
ExprKind::Loop(block, ..) => {
|
|
self.loops.push(expr.hir_id);
|
|
self.is_single_insert = false;
|
|
self.allow_insert_closure &= !self.in_tail_pos;
|
|
// Don't allow insertions inside of a loop.
|
|
let edit_len = self.edits.len();
|
|
self.visit_block(block);
|
|
if self.edits.len() != edit_len {
|
|
self.can_use_entry = false;
|
|
}
|
|
self.loops.pop();
|
|
},
|
|
ExprKind::Block(block, _) => self.visit_block(block),
|
|
ExprKind::InlineAsm(_) => {
|
|
self.can_use_entry = false;
|
|
},
|
|
_ => {
|
|
self.allow_insert_closure &= !self.in_tail_pos;
|
|
self.allow_insert_closure &=
|
|
can_move_expr_to_closure_no_visit(self.cx, expr, &self.loops, &self.locals);
|
|
// Sub expressions are no longer in the tail position.
|
|
self.is_single_insert = false;
|
|
self.in_tail_pos = false;
|
|
walk_expr(self, expr);
|
|
},
|
|
},
|
|
}
|
|
}
|
|
|
|
fn visit_pat(&mut self, p: &'tcx Pat<'tcx>) {
|
|
p.each_binding_or_first(&mut |_, id, _, _| {
|
|
self.locals.insert(id);
|
|
});
|
|
}
|
|
}
|
|
|
|
struct InsertSearchResults<'tcx> {
|
|
edits: Vec<Edit<'tcx>>,
|
|
allow_insert_closure: bool,
|
|
is_single_insert: bool,
|
|
}
|
|
impl<'tcx> InsertSearchResults<'tcx> {
|
|
fn as_single_insertion(&self) -> Option<Insertion<'tcx>> {
|
|
self.is_single_insert.then(|| self.edits[0].as_insertion().unwrap())
|
|
}
|
|
|
|
fn snippet(
|
|
&self,
|
|
cx: &LateContext<'_>,
|
|
mut span: Span,
|
|
app: &mut Applicability,
|
|
write_wrapped: impl Fn(&mut String, Insertion<'_>, SyntaxContext, &mut Applicability),
|
|
) -> String {
|
|
let ctxt = span.ctxt();
|
|
let mut res = String::new();
|
|
for insertion in self.edits.iter().filter_map(|e| e.as_insertion()) {
|
|
res.push_str(&snippet_with_applicability(
|
|
cx,
|
|
span.until(insertion.call.span),
|
|
"..",
|
|
app,
|
|
));
|
|
if is_expr_used_or_unified(cx.tcx, insertion.call) {
|
|
write_wrapped(&mut res, insertion, ctxt, app);
|
|
} else {
|
|
let _: fmt::Result = write!(
|
|
res,
|
|
"e.insert({})",
|
|
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
|
|
);
|
|
}
|
|
span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
|
|
}
|
|
res.push_str(&snippet_with_applicability(cx, span, "..", app));
|
|
res
|
|
}
|
|
|
|
fn snippet_occupied(&self, cx: &LateContext<'_>, span: Span, app: &mut Applicability) -> (String, &'static str) {
|
|
(
|
|
self.snippet(cx, span, app, |res, insertion, ctxt, app| {
|
|
// Insertion into a map would return `Some(&mut value)`, but the entry returns `&mut value`
|
|
let _: fmt::Result = write!(
|
|
res,
|
|
"Some(e.insert({}))",
|
|
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
|
|
);
|
|
}),
|
|
"Occupied(mut e)",
|
|
)
|
|
}
|
|
|
|
fn snippet_vacant(&self, cx: &LateContext<'_>, span: Span, app: &mut Applicability) -> (String, &'static str) {
|
|
(
|
|
self.snippet(cx, span, app, |res, insertion, ctxt, app| {
|
|
// Insertion into a map would return `None`, but the entry returns a mutable reference.
|
|
let _: fmt::Result = if is_expr_final_block_expr(cx.tcx, insertion.call) {
|
|
write!(
|
|
res,
|
|
"e.insert({});\n{}None",
|
|
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
|
|
snippet_indent(cx, insertion.call.span).as_deref().unwrap_or(""),
|
|
)
|
|
} else {
|
|
write!(
|
|
res,
|
|
"{{ e.insert({}); None }}",
|
|
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
|
|
)
|
|
};
|
|
}),
|
|
"Vacant(e)",
|
|
)
|
|
}
|
|
|
|
fn snippet_closure(&self, cx: &LateContext<'_>, mut span: Span, app: &mut Applicability) -> String {
|
|
let ctxt = span.ctxt();
|
|
let mut res = String::new();
|
|
for edit in &self.edits {
|
|
match *edit {
|
|
Edit::Insertion(insertion) => {
|
|
// Cut out the value from `map.insert(key, value)`
|
|
res.push_str(&snippet_with_applicability(
|
|
cx,
|
|
span.until(insertion.call.span),
|
|
"..",
|
|
app,
|
|
));
|
|
res.push_str(&snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0);
|
|
span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
|
|
},
|
|
Edit::RemoveSemi(semi_span) => {
|
|
// Cut out the semicolon. This allows the value to be returned from the closure.
|
|
res.push_str(&snippet_with_applicability(cx, span.until(semi_span), "..", app));
|
|
span = span.trim_start(semi_span).unwrap_or(DUMMY_SP);
|
|
},
|
|
}
|
|
}
|
|
res.push_str(&snippet_with_applicability(cx, span, "..", app));
|
|
res
|
|
}
|
|
}
|
|
|
|
fn find_insert_calls<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
contains_expr: &ContainsExpr<'tcx>,
|
|
expr: &'tcx Expr<'_>,
|
|
) -> Option<InsertSearchResults<'tcx>> {
|
|
let mut s = InsertSearcher {
|
|
cx,
|
|
map: contains_expr.map,
|
|
key: contains_expr.key,
|
|
ctxt: expr.span.ctxt(),
|
|
edits: Vec::new(),
|
|
is_map_used: false,
|
|
allow_insert_closure: true,
|
|
can_use_entry: true,
|
|
in_tail_pos: true,
|
|
is_single_insert: true,
|
|
loops: Vec::new(),
|
|
locals: HirIdSet::default(),
|
|
};
|
|
s.visit_expr(expr);
|
|
let allow_insert_closure = s.allow_insert_closure;
|
|
let is_single_insert = s.is_single_insert;
|
|
let edits = s.edits;
|
|
s.can_use_entry.then_some(InsertSearchResults {
|
|
edits,
|
|
allow_insert_closure,
|
|
is_single_insert,
|
|
})
|
|
}
|