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use crate::utils::SpanlessEq;
use crate::utils::{get_item_name, higher, match_type, paths, snippet, snippet_opt};
use crate::utils::{snippet_with_applicability, span_lint_and_then, walk_ptrs_ty};
use if_chain::if_chain;
use rustc::hir::map::Map;
use rustc_errors::Applicability;
use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
use rustc_hir::*;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
declare_clippy_lint! {
/// **What it does:** Checks for uses of `contains_key` + `insert` on `HashMap`
/// or `BTreeMap`.
///
/// **Why is this bad?** Using `entry` is more efficient.
///
/// **Known problems:** Some false negatives, eg.:
/// ```rust
/// # use std::collections::HashMap;
/// # let mut map = HashMap::new();
/// # let v = 1;
/// # let k = 1;
/// if !map.contains_key(&k) {
/// map.insert(k.clone(), v);
/// }
/// ```
///
/// **Example:**
/// ```rust
/// # use std::collections::HashMap;
/// # let mut map = HashMap::new();
/// # let k = 1;
/// # let v = 1;
/// if !map.contains_key(&k) {
/// map.insert(k, v);
/// }
/// ```
/// can both be rewritten as:
/// ```rust
/// # use std::collections::HashMap;
/// # let mut map = HashMap::new();
/// # let k = 1;
/// # let v = 1;
/// map.entry(k).or_insert(v);
/// ```
pub MAP_ENTRY,
perf,
"use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
}
declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HashMapPass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
if let Some((ref check, ref then_block, ref else_block)) = higher::if_block(&expr) {
if let ExprKind::Unary(UnOp::UnNot, ref check) = check.kind {
if let Some((ty, map, key)) = check_cond(cx, check) {
// in case of `if !m.contains_key(&k) { m.insert(k, v); }`
// we can give a better error message
let sole_expr = {
else_block.is_none()
&& if let ExprKind::Block(ref then_block, _) = then_block.kind {
(then_block.expr.is_some() as usize) + then_block.stmts.len() == 1
} else {
true
}
// XXXManishearth we can also check for if/else blocks containing `None`.
};
let mut visitor = InsertVisitor {
cx,
span: expr.span,
ty,
map,
key,
sole_expr,
};
walk_expr(&mut visitor, &**then_block);
}
} else if let Some(ref else_block) = *else_block {
if let Some((ty, map, key)) = check_cond(cx, check) {
let mut visitor = InsertVisitor {
cx,
span: expr.span,
ty,
map,
key,
sole_expr: false,
};
walk_expr(&mut visitor, else_block);
}
}
}
}
}
fn check_cond<'a, 'tcx, 'b>(
cx: &'a LateContext<'a, 'tcx>,
check: &'b Expr<'b>,
) -> Option<(&'static str, &'b Expr<'b>, &'b Expr<'b>)> {
if_chain! {
if let ExprKind::MethodCall(ref path, _, ref params) = check.kind;
if params.len() >= 2;
if path.ident.name == sym!(contains_key);
if let ExprKind::AddrOf(BorrowKind::Ref, _, ref key) = params[1].kind;
then {
let map = ¶ms[0];
let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(map));
return if match_type(cx, obj_ty, &paths::BTREEMAP) {
Some(("BTreeMap", map, key))
}
else if match_type(cx, obj_ty, &paths::HASHMAP) {
Some(("HashMap", map, key))
}
else {
None
};
}
}
None
}
struct InsertVisitor<'a, 'tcx, 'b> {
cx: &'a LateContext<'a, 'tcx>,
span: Span,
ty: &'static str,
map: &'b Expr<'b>,
key: &'b Expr<'b>,
sole_expr: bool,
}
impl<'a, 'tcx, 'b> Visitor<'tcx> for InsertVisitor<'a, 'tcx, 'b> {
type Map = Map<'tcx>;
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if_chain! {
if let ExprKind::MethodCall(ref path, _, ref params) = expr.kind;
if params.len() == 3;
if path.ident.name == sym!(insert);
if get_item_name(self.cx, self.map) == get_item_name(self.cx, ¶ms[0]);
if SpanlessEq::new(self.cx).eq_expr(self.key, ¶ms[1]);
if snippet_opt(self.cx, self.map.span) == snippet_opt(self.cx, params[0].span);
then {
span_lint_and_then(self.cx, MAP_ENTRY, self.span,
&format!("usage of `contains_key` followed by `insert` on a `{}`", self.ty), |db| {
if self.sole_expr {
let mut app = Applicability::MachineApplicable;
let help = format!("{}.entry({}).or_insert({});",
snippet_with_applicability(self.cx, self.map.span, "map", &mut app),
snippet_with_applicability(self.cx, params[1].span, "..", &mut app),
snippet_with_applicability(self.cx, params[2].span, "..", &mut app));
db.span_suggestion(
self.span,
"consider using",
help,
Applicability::MachineApplicable, // snippet
);
}
else {
let help = format!("consider using `{}.entry({})`",
snippet(self.cx, self.map.span, "map"),
snippet(self.cx, params[1].span, ".."));
db.span_label(
self.span,
&help,
);
}
});
}
}
if !self.sole_expr {
walk_expr(self, expr);
}
}
fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
NestedVisitorMap::None
}
}
|
