[map_identity]: recognize tuples

tests/ui/map_identity.fixed

@@ -22,6 +22,30 @@ fn main() {
     let _ = Ok(1).map_err(std::convert::identity::<u32>);
 }
 
+fn issue7189() {
+    // should lint
+    let x = [(1, 2), (3, 4)];
+    let _ = x.iter();
+    let _ = x.iter();
+    let _ = x.iter();
+
+    let y = [(1, 2, (3, (4,))), (5, 6, (7, (8,)))];
+    let _ = y.iter();
+
+    // should not lint
+    let _ = x.iter().map(|(x, y)| (x, y, y));
+    let _ = x.iter().map(|(x, _y)| (x,));
+    let _ = x.iter().map(|(x, _)| (x,));
+    let _ = x.iter().map(|(x, ..)| (x,));
+    let _ = y.iter().map(|(x, y, (z, _))| (x, y, (z, z)));
+    let _ = y
+        .iter()
+        .map(|(x, y, (z, _)): &(i32, i32, (i32, (i32,)))| (x, y, (z, z)));
+    let _ = y
+        .iter()
+        .map(|(x, y, (z, (w,))): &(i32, i32, (i32, (i32,)))| (x, y, (z, (w,))));
+}
+
 fn not_identity(x: &u16) -> u16 {
     *x
 }

tests/ui/map_identity.rs

@@ -24,6 +24,32 @@ fn main() {
     let _ = Ok(1).map_err(std::convert::identity::<u32>);
 }
 
+fn issue7189() {
+    // should lint
+    let x = [(1, 2), (3, 4)];
+    let _ = x.iter().map(|(x, y)| (x, y));
+    let _ = x.iter().map(|(x, y)| {
+        return (x, y);
+    });
+    let _ = x.iter().map(|(x, y)| return (x, y));
+
+    let y = [(1, 2, (3, (4,))), (5, 6, (7, (8,)))];
+    let _ = y.iter().map(|(x, y, (z, (w,)))| (x, y, (z, (w,))));
+
+    // should not lint
+    let _ = x.iter().map(|(x, y)| (x, y, y));
+    let _ = x.iter().map(|(x, _y)| (x,));
+    let _ = x.iter().map(|(x, _)| (x,));
+    let _ = x.iter().map(|(x, ..)| (x,));
+    let _ = y.iter().map(|(x, y, (z, _))| (x, y, (z, z)));
+    let _ = y
+        .iter()
+        .map(|(x, y, (z, _)): &(i32, i32, (i32, (i32,)))| (x, y, (z, z)));
+    let _ = y
+        .iter()
+        .map(|(x, y, (z, (w,))): &(i32, i32, (i32, (i32,)))| (x, y, (z, (w,))));
+}
+
 fn not_identity(x: &u16) -> u16 {
     *x
 }

tests/ui/map_identity.stderr

@@ -40,5 +40,32 @@ error: unnecessary map of the identity function
 LL |     let _: Result<u32, u32> = Ok(1).map_err(|a| a);
    |                                    ^^^^^^^^^^^^^^^ help: remove the call to `map_err`
 
-error: aborting due to 6 previous errors
+error: unnecessary map of the identity function
+  --> $DIR/map_identity.rs:30:21
+   |
+LL |     let _ = x.iter().map(|(x, y)| (x, y));
+   |                     ^^^^^^^^^^^^^^^^^^^^^ help: remove the call to `map`
+
+error: unnecessary map of the identity function
+  --> $DIR/map_identity.rs:31:21
+   |
+LL |       let _ = x.iter().map(|(x, y)| {
+   |  _____________________^
+LL | |         return (x, y);
+LL | |     });
+   | |______^ help: remove the call to `map`
+
+error: unnecessary map of the identity function
+  --> $DIR/map_identity.rs:34:21
+   |
+LL |     let _ = x.iter().map(|(x, y)| return (x, y));
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the call to `map`
+
+error: unnecessary map of the identity function
+  --> $DIR/map_identity.rs:37:21
+   |
+LL |     let _ = y.iter().map(|(x, y, (z, (w,)))| (x, y, (z, (w,))));
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the call to `map`
+
+error: aborting due to 10 previous errors