map_entry: don't suggest when {e.insert(_); None } would be required

Author: ada4a

clippy_lints/src/entry.rs

@@ -90,4 +90,11 @@ mod issue13306 {
     }
 }
 
+fn issue15307<K: Eq + Hash, V>(mut m: HashMap<K, V>, k: K, v: V) {
+    if !m.contains_key(&k) {
+        //~^ map_entry
+        assert!(m.insert(k, v).is_none());
+    }
+}
+
 fn main() {}

tests/ui/entry_unfixable.rs

@@ -42,5 +42,16 @@ LL | |             }
    |
    = help: consider using the `Entry` API: https://doc.rust-lang.org/std/collections/struct.HashMap.html#entry-api
 
-error: aborting due to 3 previous errors
+error: usage of `contains_key` followed by `insert` on a `HashMap`
+  --> tests/ui/entry_unfixable.rs:94:5
+   |
+LL | /     if !m.contains_key(&k) {
+LL | |
+LL | |         assert!(m.insert(k, v).is_none());
+LL | |     }
+   | |_____^
+   |
+   = help: consider using the `Entry` API: https://doc.rust-lang.org/std/collections/struct.HashMap.html#entry-api
+
+error: aborting due to 4 previous errors
 

tests/ui/entry_unfixable.stderr

@@ -55,17 +55,6 @@ fn insert_if_absent0<K: Eq + Hash + Copy, V: Copy>(m: &mut HashMap<K, V>, k: K,
         }
     }
 
-    match m.entry(k) {
-        std::collections::hash_map::Entry::Occupied(mut e) => {
-            //~^ map_entry
-            if true { Some(e.insert(v)) } else { Some(e.insert(v2)) }
-        }
-        std::collections::hash_map::Entry::Vacant(e) => {
-            e.insert(v);
-            None
-        }
-    };
-
     if let std::collections::hash_map::Entry::Occupied(mut e) = m.entry(k) {
         //~^ map_entry
         foo();

tests/ui/entry_with_else.fixed

@@ -46,13 +46,6 @@ fn insert_if_absent0<K: Eq + Hash + Copy, V: Copy>(m: &mut HashMap<K, V>, k: K,
         m.insert(k, v2);
     }
 
-    if m.contains_key(&k) {
-        //~^ map_entry
-        if true { m.insert(k, v) } else { m.insert(k, v2) }
-    } else {
-        m.insert(k, v)
-    };
-
     if m.contains_key(&k) {
         //~^ map_entry
         foo();

tests/ui/entry_with_else.rs

@@ -119,31 +119,6 @@ error: usage of `contains_key` followed by `insert` on a `HashMap`
    |
 LL | /     if m.contains_key(&k) {
 LL | |
-LL | |         if true { m.insert(k, v) } else { m.insert(k, v2) }
-LL | |     } else {
-LL | |         m.insert(k, v)
-LL | |     };
-   | |_____^
-   |
-help: try
-   |
-LL ~     match m.entry(k) {
-LL +         std::collections::hash_map::Entry::Occupied(mut e) => {
-LL +
-LL +             if true { Some(e.insert(v)) } else { Some(e.insert(v2)) }
-LL +         }
-LL +         std::collections::hash_map::Entry::Vacant(e) => {
-LL +             e.insert(v);
-LL +             None
-LL +         }
-LL ~     };
-   |
-
-error: usage of `contains_key` followed by `insert` on a `HashMap`
-  --> tests/ui/entry_with_else.rs:56:5
-   |
-LL | /     if m.contains_key(&k) {
-LL | |
 LL | |         foo();
 LL | |         m.insert(k, v)
 LL | |     } else {
@@ -162,5 +137,5 @@ LL +         None
 LL ~     };
    |
 
-error: aborting due to 7 previous errors
+error: aborting due to 6 previous errors
 

tests/ui/entry_with_else.stderr

@@ -0,0 +1,16 @@
+//@no-rustfix
+#![warn(clippy::map_entry)]
+
+use std::collections::HashMap;
+use std::hash::Hash;
+
+fn foo() {}
+
+fn insert_if_absent0<K: Eq + Hash + Copy, V: Copy>(m: &mut HashMap<K, V>, k: K, v: V, v2: V) {
+    if m.contains_key(&k) {
+        //~^ map_entry
+        if true { m.insert(k, v) } else { m.insert(k, v2) }
+    } else {
+        m.insert(k, v)
+    };
+}

tests/ui/entry_with_else_unfixable.rs

@@ -0,0 +1,17 @@
+error: usage of `contains_key` followed by `insert` on a `HashMap`
+  --> tests/ui/entry_with_else_unfixable.rs:10:5
+   |
+LL | /     if m.contains_key(&k) {
+LL | |
+LL | |         if true { m.insert(k, v) } else { m.insert(k, v2) }
+LL | |     } else {
+LL | |         m.insert(k, v)
+LL | |     };
+   | |_____^
+   |
+   = help: consider using the `Entry` API: https://doc.rust-lang.org/std/collections/struct.HashMap.html#entry-api
+   = note: `-D clippy::map-entry` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::map_entry)]`
+
+error: aborting due to 1 previous error
+