Fix .map(..).unwrap_or_else(..) bad suggestion

clippy_lints/src/methods/mod.rs

@@ -20,6 +20,7 @@ use syntax::symbol::LocalInternedString;
 
 use crate::utils::paths;
 use crate::utils::sugg;
+use crate::utils::usage::mutated_variables;
 use crate::utils::{
     get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, implements_trait, in_macro, is_copy,
     is_ctor_function, is_expn_of, is_self, is_self_ty, iter_input_pats, last_path_segment, match_def_path, match_path,
@@ -1880,7 +1881,20 @@ fn lint_map_unwrap_or_else<'a, 'tcx>(
     // lint if the caller of `map()` is an `Option`
     let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
     let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
+
     if is_option || is_result {
+        // Don't make a suggestion that may fail to compile due to mutably borrowing
+        // the same variable twice.
+        let map_mutated_vars = mutated_variables(&map_args[0], cx);
+        let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
+        if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
+            if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
+                return;
+            }
+        } else {
+            return;
+        }
+
         // lint message
         let msg = if is_option {
             "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \

tests/ui/methods.rs

@@ -203,6 +203,21 @@ fn option_methods() {
     // Macro case.
     // Should not lint.
     let _ = opt_map!(opt, |x| x + 1).unwrap_or_else(|| 0);
+
+    // Issue #4144
+    {
+        let mut frequencies = HashMap::new();
+        let word = "foo";
+
+        frequencies
+            .get_mut(word)
+            .map(|count| {
+                *count += 1;
+            })
+            .unwrap_or_else(|| {
+                frequencies.insert(word.to_owned(), 1);
+            });
+    }
 }
 
 /// Checks implementation of `FILTER_NEXT` lint.

tests/ui/methods.stderr

@@ -130,7 +130,7 @@ LL | |                 );
    | |_________________^
 
 error: called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling `.find(p)` instead.
-  --> $DIR/methods.rs:214:13
+  --> $DIR/methods.rs:229:13
    |
 LL |     let _ = v.iter().filter(|&x| *x < 0).next();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -139,7 +139,7 @@ LL |     let _ = v.iter().filter(|&x| *x < 0).next();
    = note: replace `filter(|&x| *x < 0).next()` with `find(|&x| *x < 0)`
 
 error: called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling `.find(p)` instead.
-  --> $DIR/methods.rs:217:13
+  --> $DIR/methods.rs:232:13
    |
 LL |       let _ = v.iter().filter(|&x| {
    |  _____________^
@@ -149,7 +149,7 @@ LL | |                    ).next();
    | |___________________________^
 
 error: called `is_some()` after searching an `Iterator` with find. This is more succinctly expressed by calling `any()`.
-  --> $DIR/methods.rs:233:13
+  --> $DIR/methods.rs:248:13
    |
 LL |     let _ = v.iter().find(|&x| *x < 0).is_some();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -158,7 +158,7 @@ LL |     let _ = v.iter().find(|&x| *x < 0).is_some();
    = note: replace `find(|&x| *x < 0).is_some()` with `any(|x| *x < 0)`
 
 error: called `is_some()` after searching an `Iterator` with find. This is more succinctly expressed by calling `any()`.
-  --> $DIR/methods.rs:236:13
+  --> $DIR/methods.rs:251:13
    |
 LL |       let _ = v.iter().find(|&x| {
    |  _____________^
@@ -168,15 +168,15 @@ LL | |                    ).is_some();
    | |______________________________^
 
 error: called `is_some()` after searching an `Iterator` with position. This is more succinctly expressed by calling `any()`.
-  --> $DIR/methods.rs:242:13
+  --> $DIR/methods.rs:257:13
    |
 LL |     let _ = v.iter().position(|&x| x < 0).is_some();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: replace `position(|&x| x < 0).is_some()` with `any(|&x| x < 0)`
 
 error: called `is_some()` after searching an `Iterator` with position. This is more succinctly expressed by calling `any()`.
-  --> $DIR/methods.rs:245:13
+  --> $DIR/methods.rs:260:13
    |
 LL |       let _ = v.iter().position(|&x| {
    |  _____________^
@@ -186,15 +186,15 @@ LL | |                    ).is_some();
    | |______________________________^
 
 error: called `is_some()` after searching an `Iterator` with rposition. This is more succinctly expressed by calling `any()`.
-  --> $DIR/methods.rs:251:13
+  --> $DIR/methods.rs:266:13
    |
 LL |     let _ = v.iter().rposition(|&x| x < 0).is_some();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: replace `rposition(|&x| x < 0).is_some()` with `any(|&x| x < 0)`
 
 error: called `is_some()` after searching an `Iterator` with rposition. This is more succinctly expressed by calling `any()`.
-  --> $DIR/methods.rs:254:13
+  --> $DIR/methods.rs:269:13
    |
 LL |       let _ = v.iter().rposition(|&x| {
    |  _____________^
@@ -204,7 +204,7 @@ LL | |                    ).is_some();
    | |______________________________^
 
 error: used unwrap() on an Option value. If you don't want to handle the None case gracefully, consider using expect() to provide a better panic message
-  --> $DIR/methods.rs:269:13
+  --> $DIR/methods.rs:284:13
    |
 LL |     let _ = opt.unwrap();
    |             ^^^^^^^^^^^^