390 lines
14 KiB
Rust
390 lines
14 KiB
Rust
use std::borrow::Cow;
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use std::collections::BTreeMap;
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use rustc_errors::DiagnosticBuilder;
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use rustc_hir as hir;
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use rustc_hir::intravisit::{walk_body, walk_expr, walk_inf, walk_ty, Visitor};
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use rustc_hir::{Body, Expr, ExprKind, GenericArg, Item, ItemKind, QPath, TyKind};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::hir::nested_filter;
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use rustc_middle::lint::in_external_macro;
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use rustc_middle::ty::{Ty, TyS, TypeckResults};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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use rustc_span::symbol::sym;
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use rustc_typeck::hir_ty_to_ty;
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use if_chain::if_chain;
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use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
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use clippy_utils::differing_macro_contexts;
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use clippy_utils::source::{snippet, snippet_opt};
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use clippy_utils::ty::is_type_diagnostic_item;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for public `impl` or `fn` missing generalization
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/// over different hashers and implicitly defaulting to the default hashing
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/// algorithm (`SipHash`).
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///
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/// ### Why is this bad?
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/// `HashMap` or `HashSet` with custom hashers cannot be
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/// used with them.
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///
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/// ### Known problems
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/// Suggestions for replacing constructors can contain
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/// false-positives. Also applying suggestions can require modification of other
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/// pieces of code, possibly including external crates.
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///
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/// ### Example
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/// ```rust
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/// # use std::collections::HashMap;
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/// # use std::hash::{Hash, BuildHasher};
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/// # trait Serialize {};
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/// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
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///
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/// pub fn foo(map: &mut HashMap<i32, i32>) { }
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/// ```
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/// could be rewritten as
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/// ```rust
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/// # use std::collections::HashMap;
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/// # use std::hash::{Hash, BuildHasher};
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/// # trait Serialize {};
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/// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
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///
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/// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub IMPLICIT_HASHER,
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pedantic,
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"missing generalization over different hashers"
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}
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declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
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impl<'tcx> LateLintPass<'tcx> for ImplicitHasher {
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#[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
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use rustc_span::BytePos;
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fn suggestion<'tcx>(
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cx: &LateContext<'tcx>,
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diag: &mut DiagnosticBuilder<'_>,
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generics_span: Span,
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generics_suggestion_span: Span,
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target: &ImplicitHasherType<'_>,
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vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
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) {
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let generics_snip = snippet(cx, generics_span, "");
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// trim `<` `>`
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let generics_snip = if generics_snip.is_empty() {
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""
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} else {
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&generics_snip[1..generics_snip.len() - 1]
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};
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multispan_sugg(
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diag,
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"consider adding a type parameter",
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vec![
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(
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generics_suggestion_span,
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format!(
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"<{}{}S: ::std::hash::BuildHasher{}>",
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generics_snip,
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if generics_snip.is_empty() { "" } else { ", " },
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if vis.suggestions.is_empty() {
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""
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} else {
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// request users to add `Default` bound so that generic constructors can be used
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" + Default"
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},
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),
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),
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(
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target.span(),
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format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
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),
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],
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);
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if !vis.suggestions.is_empty() {
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multispan_sugg(diag, "...and use generic constructor", vis.suggestions);
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}
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}
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if !cx.access_levels.is_exported(item.def_id) {
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return;
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}
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match item.kind {
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ItemKind::Impl(ref impl_) => {
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let mut vis = ImplicitHasherTypeVisitor::new(cx);
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vis.visit_ty(impl_.self_ty);
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for target in &vis.found {
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if differing_macro_contexts(item.span, target.span()) {
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return;
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}
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let generics_suggestion_span = impl_.generics.span.substitute_dummy({
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let pos = snippet_opt(cx, item.span.until(target.span()))
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.and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
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if let Some(pos) = pos {
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Span::new(pos, pos, item.span.ctxt(), item.span.parent())
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} else {
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return;
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}
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});
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let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
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for item in impl_.items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
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ctr_vis.visit_impl_item(item);
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}
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span_lint_and_then(
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cx,
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IMPLICIT_HASHER,
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target.span(),
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&format!(
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"impl for `{}` should be generalized over different hashers",
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target.type_name()
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),
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move |diag| {
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suggestion(cx, diag, impl_.generics.span, generics_suggestion_span, target, ctr_vis);
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},
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);
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}
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},
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ItemKind::Fn(ref sig, ref generics, body_id) => {
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let body = cx.tcx.hir().body(body_id);
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for ty in sig.decl.inputs {
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let mut vis = ImplicitHasherTypeVisitor::new(cx);
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vis.visit_ty(ty);
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for target in &vis.found {
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if in_external_macro(cx.sess(), generics.span) {
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continue;
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}
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let generics_suggestion_span = generics.span.substitute_dummy({
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let pos = snippet_opt(
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cx,
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Span::new(
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item.span.lo(),
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body.params[0].pat.span.lo(),
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item.span.ctxt(),
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item.span.parent(),
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),
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)
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.and_then(|snip| {
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let i = snip.find("fn")?;
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Some(item.span.lo() + BytePos((i + snip[i..].find('(')?) as u32))
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})
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.expect("failed to create span for type parameters");
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Span::new(pos, pos, item.span.ctxt(), item.span.parent())
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});
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let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
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ctr_vis.visit_body(body);
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span_lint_and_then(
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cx,
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IMPLICIT_HASHER,
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target.span(),
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&format!(
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"parameter of type `{}` should be generalized over different hashers",
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target.type_name()
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),
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move |diag| {
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suggestion(cx, diag, generics.span, generics_suggestion_span, target, ctr_vis);
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},
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);
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}
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}
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},
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_ => {},
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}
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}
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}
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enum ImplicitHasherType<'tcx> {
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HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
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HashSet(Span, Ty<'tcx>, Cow<'static, str>),
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}
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impl<'tcx> ImplicitHasherType<'tcx> {
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/// Checks that `ty` is a target type without a `BuildHasher`.
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fn new(cx: &LateContext<'tcx>, hir_ty: &hir::Ty<'_>) -> Option<Self> {
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if let TyKind::Path(QPath::Resolved(None, path)) = hir_ty.kind {
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let params: Vec<_> = path
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.segments
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.last()
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.as_ref()?
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.args
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.as_ref()?
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.args
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.iter()
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.filter_map(|arg| match arg {
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GenericArg::Type(ty) => Some(ty),
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_ => None,
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})
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.collect();
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let params_len = params.len();
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let ty = hir_ty_to_ty(cx.tcx, hir_ty);
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if is_type_diagnostic_item(cx, ty, sym::HashMap) && params_len == 2 {
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Some(ImplicitHasherType::HashMap(
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hir_ty.span,
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ty,
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snippet(cx, params[0].span, "K"),
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snippet(cx, params[1].span, "V"),
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))
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} else if is_type_diagnostic_item(cx, ty, sym::HashSet) && params_len == 1 {
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Some(ImplicitHasherType::HashSet(
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hir_ty.span,
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ty,
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snippet(cx, params[0].span, "T"),
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))
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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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fn type_name(&self) -> &'static str {
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match *self {
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ImplicitHasherType::HashMap(..) => "HashMap",
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ImplicitHasherType::HashSet(..) => "HashSet",
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}
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}
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fn type_arguments(&self) -> String {
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match *self {
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ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
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ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
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}
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}
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fn ty(&self) -> Ty<'tcx> {
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match *self {
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ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
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}
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}
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fn span(&self) -> Span {
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match *self {
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ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
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}
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}
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}
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struct ImplicitHasherTypeVisitor<'a, 'tcx> {
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cx: &'a LateContext<'tcx>,
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found: Vec<ImplicitHasherType<'tcx>>,
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}
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impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
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fn new(cx: &'a LateContext<'tcx>) -> Self {
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Self { cx, found: vec![] }
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}
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}
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impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
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fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
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if let Some(target) = ImplicitHasherType::new(self.cx, t) {
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self.found.push(target);
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}
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walk_ty(self, t);
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}
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fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
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if let Some(target) = ImplicitHasherType::new(self.cx, &inf.to_ty()) {
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self.found.push(target);
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}
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walk_inf(self, inf);
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}
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}
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/// Looks for default-hasher-dependent constructors like `HashMap::new`.
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struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
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cx: &'a LateContext<'tcx>,
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maybe_typeck_results: Option<&'tcx TypeckResults<'tcx>>,
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target: &'b ImplicitHasherType<'tcx>,
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suggestions: BTreeMap<Span, String>,
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}
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impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
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fn new(cx: &'a LateContext<'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
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Self {
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cx,
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maybe_typeck_results: cx.maybe_typeck_results(),
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target,
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suggestions: BTreeMap::new(),
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}
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}
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}
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impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
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type NestedFilter = nested_filter::OnlyBodies;
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fn visit_body(&mut self, body: &'tcx Body<'_>) {
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let old_maybe_typeck_results = self.maybe_typeck_results.replace(self.cx.tcx.typeck_body(body.id()));
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walk_body(self, body);
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self.maybe_typeck_results = old_maybe_typeck_results;
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}
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fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
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if_chain! {
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if let ExprKind::Call(fun, args) = e.kind;
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if let ExprKind::Path(QPath::TypeRelative(ty, method)) = fun.kind;
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if let TyKind::Path(QPath::Resolved(None, ty_path)) = ty.kind;
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if let Some(ty_did) = ty_path.res.opt_def_id();
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then {
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if !TyS::same_type(self.target.ty(), self.maybe_typeck_results.unwrap().expr_ty(e)) {
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return;
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}
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if self.cx.tcx.is_diagnostic_item(sym::HashMap, ty_did) {
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if method.ident.name == sym::new {
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self.suggestions
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.insert(e.span, "HashMap::default()".to_string());
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} else if method.ident.name == sym!(with_capacity) {
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self.suggestions.insert(
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e.span,
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format!(
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"HashMap::with_capacity_and_hasher({}, Default::default())",
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snippet(self.cx, args[0].span, "capacity"),
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),
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);
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}
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} else if self.cx.tcx.is_diagnostic_item(sym::HashSet, ty_did) {
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if method.ident.name == sym::new {
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self.suggestions
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.insert(e.span, "HashSet::default()".to_string());
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} else if method.ident.name == sym!(with_capacity) {
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self.suggestions.insert(
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e.span,
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format!(
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"HashSet::with_capacity_and_hasher({}, Default::default())",
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snippet(self.cx, args[0].span, "capacity"),
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),
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);
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}
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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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fn nested_visit_map(&mut self) -> Self::Map {
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self.cx.tcx.hir()
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}
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}
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