Add Iterator::map to useless_conversion

Author: samueltardieu

clippy_lints/src/useless_conversion.rs

@@ -434,5 +434,8 @@ fn has_eligible_receiver(cx: &LateContext<'_>, recv: &Expr<'_>, expr: &Expr<'_>)
             return true;
         }
     }
+    if is_trait_method(cx, expr, sym::Iterator) {
+        return true;
+    }
     false
 }

tests/ui/useless_conversion.fixed

@@ -328,11 +328,17 @@ fn direct_application() {
             Self
         }
     }
+    let _: Vec<u32> = [1u32].into_iter().collect();
+    //~^ useless_conversion
 
     // No lint for those
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(Into::into);
     let _: Result<(), Absorb> = test_issue_3913().map_err(Into::into);
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(From::from);
     let _: Result<(), Absorb> = test_issue_3913().map_err(From::from);
-    let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+}
+
+fn gen_identity<T>(x: [T; 3]) -> Vec<T> {
+    x.into_iter().collect()
+    //~^ useless_conversion
 }

tests/ui/useless_conversion.rs

@@ -328,11 +328,17 @@ fn direct_application() {
             Self
         }
     }
+    let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+    //~^ useless_conversion
 
     // No lint for those
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(Into::into);
     let _: Result<(), Absorb> = test_issue_3913().map_err(Into::into);
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(From::from);
     let _: Result<(), Absorb> = test_issue_3913().map_err(From::from);
-    let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+}
+
+fn gen_identity<T>(x: [T; 3]) -> Vec<T> {
+    x.into_iter().map(Into::into).collect()
+    //~^ useless_conversion
 }

tests/ui/useless_conversion.stderr

@@ -262,5 +262,17 @@ error: useless conversion to the same type: `()`
 LL |     let _: ControlFlow<()> = c.map_continue(Into::into);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing
 
-error: aborting due to 34 previous errors
+error: useless conversion to the same type: `u32`
+  --> tests/ui/useless_conversion.rs:331:41
+   |
+LL |     let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+   |                                         ^^^^^^^^^^^^^^^^ help: consider removing
+
+error: useless conversion to the same type: `T`
+  --> tests/ui/useless_conversion.rs:342:18
+   |
+LL |     x.into_iter().map(Into::into).collect()
+   |                  ^^^^^^^^^^^^^^^^ help: consider removing
+
+error: aborting due to 36 previous errors