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|
use super::SAME_ITEM_PUSH;
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::path_to_local;
use clippy_utils::source::snippet_with_context;
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
use if_chain::if_chain;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::Applicability;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_hir::{BindingAnnotation, Block, Expr, ExprKind, HirId, Mutability, Node, Pat, PatKind, Stmt, StmtKind};
use rustc_lint::LateContext;
use rustc_span::symbol::sym;
use rustc_span::SyntaxContext;
use std::iter::Iterator;
/// Detects for loop pushing the same item into a Vec
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
pat: &'tcx Pat<'_>,
_: &'tcx Expr<'_>,
body: &'tcx Expr<'_>,
_: &'tcx Expr<'_>,
) {
fn emit_lint(cx: &LateContext<'_>, vec: &Expr<'_>, pushed_item: &Expr<'_>, ctxt: SyntaxContext) {
let mut app = Applicability::Unspecified;
let vec_str = snippet_with_context(cx, vec.span, ctxt, "", &mut app).0;
let item_str = snippet_with_context(cx, pushed_item.span, ctxt, "", &mut app).0;
span_lint_and_help(
cx,
SAME_ITEM_PUSH,
vec.span,
"it looks like the same item is being pushed into this Vec",
None,
&format!("try using vec![{item_str};SIZE] or {vec_str}.resize(NEW_SIZE, {item_str})"),
);
}
if !matches!(pat.kind, PatKind::Wild) {
return;
}
// Determine whether it is safe to lint the body
let mut same_item_push_visitor = SameItemPushVisitor::new(cx);
walk_expr(&mut same_item_push_visitor, body);
if_chain! {
if same_item_push_visitor.should_lint();
if let Some((vec, pushed_item, ctxt)) = same_item_push_visitor.vec_push;
let vec_ty = cx.typeck_results().expr_ty(vec);
let ty = vec_ty.walk().nth(1).unwrap().expect_ty();
if cx
.tcx
.lang_items()
.clone_trait()
.map_or(false, |id| implements_trait(cx, ty, id, &[]));
then {
// Make sure that the push does not involve possibly mutating values
match pushed_item.kind {
ExprKind::Path(ref qpath) => {
match cx.qpath_res(qpath, pushed_item.hir_id) {
// immutable bindings that are initialized with literal or constant
Res::Local(hir_id) => {
let node = cx.tcx.hir().get(hir_id);
if_chain! {
if let Node::Pat(pat) = node;
if let PatKind::Binding(bind_ann, ..) = pat.kind;
if !matches!(bind_ann, BindingAnnotation(_, Mutability::Mut));
let parent_node = cx.tcx.hir().parent_id(hir_id);
if let Some(Node::Local(parent_let_expr)) = cx.tcx.hir().find(parent_node);
if let Some(init) = parent_let_expr.init;
then {
match init.kind {
// immutable bindings that are initialized with literal
ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item, ctxt),
// immutable bindings that are initialized with constant
ExprKind::Path(ref path) => {
if let Res::Def(DefKind::Const, ..) = cx.qpath_res(path, init.hir_id) {
emit_lint(cx, vec, pushed_item, ctxt);
}
}
_ => {},
}
}
}
},
// constant
Res::Def(DefKind::Const, ..) => emit_lint(cx, vec, pushed_item, ctxt),
_ => {},
}
},
ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item, ctxt),
_ => {},
}
}
}
}
// Scans the body of the for loop and determines whether lint should be given
struct SameItemPushVisitor<'a, 'tcx> {
non_deterministic_expr: bool,
multiple_pushes: bool,
// this field holds the last vec push operation visited, which should be the only push seen
vec_push: Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>, SyntaxContext)>,
cx: &'a LateContext<'tcx>,
used_locals: FxHashSet<HirId>,
}
impl<'a, 'tcx> SameItemPushVisitor<'a, 'tcx> {
fn new(cx: &'a LateContext<'tcx>) -> Self {
Self {
non_deterministic_expr: false,
multiple_pushes: false,
vec_push: None,
cx,
used_locals: FxHashSet::default(),
}
}
fn should_lint(&self) -> bool {
if_chain! {
if !self.non_deterministic_expr;
if !self.multiple_pushes;
if let Some((vec, _, _)) = self.vec_push;
if let Some(hir_id) = path_to_local(vec);
then {
!self.used_locals.contains(&hir_id)
} else {
false
}
}
}
}
impl<'a, 'tcx> Visitor<'tcx> for SameItemPushVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
match &expr.kind {
// Non-determinism may occur ... don't give a lint
ExprKind::Loop(..) | ExprKind::Match(..) | ExprKind::If(..) => self.non_deterministic_expr = true,
ExprKind::Block(block, _) => self.visit_block(block),
_ => {
if let Some(hir_id) = path_to_local(expr) {
self.used_locals.insert(hir_id);
}
walk_expr(self, expr);
},
}
}
fn visit_block(&mut self, b: &'tcx Block<'_>) {
for stmt in b.stmts.iter() {
self.visit_stmt(stmt);
}
}
fn visit_stmt(&mut self, s: &'tcx Stmt<'_>) {
let vec_push_option = get_vec_push(self.cx, s);
if vec_push_option.is_none() {
// Current statement is not a push so visit inside
match &s.kind {
StmtKind::Expr(expr) | StmtKind::Semi(expr) => self.visit_expr(expr),
_ => {},
}
} else {
// Current statement is a push ...check whether another
// push had been previously done
if self.vec_push.is_none() {
self.vec_push = vec_push_option;
} else {
// There are multiple pushes ... don't lint
self.multiple_pushes = true;
}
}
}
}
// Given some statement, determine if that statement is a push on a Vec. If it is, return
// the Vec being pushed into and the item being pushed
fn get_vec_push<'tcx>(
cx: &LateContext<'tcx>,
stmt: &'tcx Stmt<'_>,
) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>, SyntaxContext)> {
if_chain! {
// Extract method being called
if let StmtKind::Semi(semi_stmt) = &stmt.kind;
if let ExprKind::MethodCall(path, self_expr, args, _) = &semi_stmt.kind;
// Figure out the parameters for the method call
if let Some(pushed_item) = args.get(0);
// Check that the method being called is push() on a Vec
if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(self_expr), sym::Vec);
if path.ident.name.as_str() == "push";
then {
return Some((self_expr, pushed_item, semi_stmt.span.ctxt()))
}
}
None
}
|
