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Finish the HashMapLint

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This commit is contained in:
mcarton 2016-01-03 16:31:28 +01:00
parent 54b70ed8e1
commit d0bb71e6a2
2 changed files with 23 additions and 15 deletions
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34
src/hashmap.rs
View File

@ -1,14 +1,18 @@
use rustc::lint::*;
use rustc_front::hir::*;
use syntax::codemap::Span;
use utils::{get_item_name, match_type, snippet, span_help_and_lint, walk_ptrs_ty};
use utils::{get_item_name, is_exp_equal, match_type, snippet, span_help_and_lint, walk_ptrs_ty};
use utils::HASHMAP_PATH;
/// **What it does:** This lint checks for uses of `contains_key` + `insert` on `HashMap`.
///
/// **Why is this bad?** Using `HashMap::entry` is more efficient.
///
/// **Known problems:** Hopefully none.
/// **Known problems:** Some false negatives, eg.:
/// ```
/// let k = &key;
/// if !m.contains_key(k) { m.insert(k.clone(), v); }
/// ```
///
/// **Example:** `if !m.contains_key(&k) { m.insert(k, v) }`
declare_lint! {
@ -36,16 +40,22 @@ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
params.len() >= 2,
name.node.as_str() == "contains_key"
], {
let key = match params[1].node {
ExprAddrOf(_, ref key) => key,
_ => return
};
let map = &params[0];
let obj_ty = walk_ptrs_ty(cx.tcx.expr_ty(map));
if match_type(cx, obj_ty, &HASHMAP_PATH) {
if let Some(ref then) = then.expr {
check_for_insert(cx, expr.span, map, then);
check_for_insert(cx, expr.span, map, key, then);
}
else if then.stmts.len() == 1 {
if let StmtSemi(ref stmt, _) = then.stmts[0].node {
check_for_insert(cx, expr.span, map, stmt);
for stmt in &then.stmts {
if let StmtSemi(ref stmt, _) = stmt.node {
check_for_insert(cx, expr.span, map, key, stmt);
}
}
}
@ -54,20 +64,20 @@ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
}
}
fn check_for_insert(cx: &LateContext, span: Span, map: &Expr, expr: &Expr) {
fn check_for_insert(cx: &LateContext, span: Span, map: &Expr, key: &Expr, expr: &Expr) {
if_let_chain! {
[
let ExprMethodCall(ref name, _, ref params) = expr.node,
params.len() >= 3,
params.len() == 3,
name.node.as_str() == "insert",
get_item_name(cx, map) == get_item_name(cx, &*params[0])
get_item_name(cx, map) == get_item_name(cx, &*params[0]),
is_exp_equal(cx, key, &params[1])
], {
span_help_and_lint(cx, HASHMAP_ENTRY, span,
"usage of `contains_key` followed by `insert` on `HashMap`",
&format!("Consider using `{}.entry({}).or_insert({})`",
&format!("Consider using `{}.entry({})`",
snippet(cx, map.span, ".."),
snippet(cx, params[1].span, ".."),
snippet(cx, params[2].span, "..")));
snippet(cx, params[1].span, "..")));
}
}
}

4
tests/compile-fail/hashmap.rs
View File

@ -15,11 +15,9 @@ fn insert_if_absent2<K: Eq + Hash, V>(m: &mut HashMap<K, V>, k: K, v: V) {
if !m.contains_key(&k) { m.insert(k, v) } else { None }; //~ERROR: usage of `contains_key` followed by `insert` on `HashMap`
}
/* TODO
fn insert_other_if_absent<K: Eq + Hash, V>(m: &mut HashMap<K, V>, k: K, o: K, v: V) {
if !m.contains_key(&k) { m.insert(o, v) } else { None };
if !m.contains_key(&k) { m.insert(o, v); }
}
*/
fn main() {
}