1 files changed, 207 insertions, 0 deletions
diff --git a/tests/ui/lint/unused/lint-unused-mut-variables.rs b/tests/ui/lint/unused/lint-unused-mut-variables.rs
new file mode 100644
index 00000000000..67ec7facf17
--- /dev/null
+++ b/tests/ui/lint/unused/lint-unused-mut-variables.rs
@@ -0,0 +1,207 @@
+// edition:2018
+
+// Exercise the unused_mut attribute in some positive and negative cases
+
+#![warn(unused_mut)]
+#![feature(async_closure, raw_ref_op)]
+
+async fn baz_async(
+    mut a: i32,
+    //~^ WARN: variable does not need to be mutable
+    #[allow(unused_mut)] mut b: i32,
+) {}
+fn baz(
+    mut a: i32,
+    //~^ WARN: variable does not need to be mutable
+    #[allow(unused_mut)] mut b: i32,
+    #[allow(unused_mut)] (mut c, d): (i32, i32)
+) {}
+
+struct RefStruct {}
+impl RefStruct {
+    async fn baz_async(
+        mut a: i32,
+        //~^ WARN: variable does not need to be mutable
+        #[allow(unused_mut)] mut b: i32,
+    ) {}
+    fn baz(
+        &self,
+        mut a: i32,
+        //~^ WARN: variable does not need to be mutable
+        #[allow(unused_mut)] mut b: i32,
+        #[allow(unused_mut)] (mut c, d): (i32, i32)
+    ) {}
+}
+
+trait RefTrait {
+    fn baz(
+        &self,
+        mut a: i32,
+        //~^ WARN: variable does not need to be mutable
+        #[allow(unused_mut)] mut b: i32,
+        #[allow(unused_mut)] (mut c, d): (i32, i32)
+    ) {}
+}
+impl RefTrait for () {
+    fn baz(
+        &self,
+        mut a: i32,
+        //~^ WARN: variable does not need to be mutable
+        #[allow(unused_mut)] mut b: i32,
+        #[allow(unused_mut)] (mut c, d): (i32, i32)
+    ) {}
+}
+
+fn main() {
+    let _ = async move |
+        mut a: i32,
+        //~^ WARN: variable does not need to be mutable
+        #[allow(unused_mut)] mut b: i32,
+    | {};
+    let _ = |
+        mut a: i32,
+        //~^ WARN: variable does not need to be mutable
+        #[allow(unused_mut)] mut b: i32,
+        #[allow(unused_mut)] (mut c, d): (i32, i32)
+    | {};
+
+    // negative cases
+    let mut a = 3; //~ WARN: variable does not need to be mutable
+
+    let mut a = 2; //~ WARN: variable does not need to be mutable
+
+    let mut b = 3; //~ WARN: variable does not need to be mutable
+
+    let mut a = vec![3]; //~ WARN: variable does not need to be mutable
+
+    let (mut a, b) = (1, 2); //~ WARN: variable does not need to be mutable
+
+    let mut a; //~ WARN: variable does not need to be mutable
+
+    a = 3;
+
+    let mut b; //~ WARN: variable does not need to be mutable
+
+    if true {
+        b = 3;
+    } else {
+        b = 4;
+    }
+
+    match 30 {
+        mut x => {} //~ WARN: variable does not need to be mutable
+
+    }
+
+    match (30, 2) {
+        // FIXME: Here's a false positive,
+        // shouldn't be removed `mut` not to be bound with a different way.
+        (mut x, 1) | //~ WARN: variable does not need to be mutable
+
+        (mut x, 2) |
+        (mut x, 3) => {
+        }
+        _ => {}
+    }
+
+    let x = |mut y: isize| 10; //~ WARN: variable does not need to be mutable
+
+    fn what(mut foo: isize) {} //~ WARN: variable does not need to be mutable
+
+
+    let mut a = &mut 5; //~ WARN: variable does not need to be mutable
+
+    *a = 4;
+
+    let mut a = 5;
+    let mut b = (&mut a,); //~ WARN: variable does not need to be mutable
+    *b.0 = 4;
+
+    let mut x = &mut 1; //~ WARN: variable does not need to be mutable
+
+    let mut f = || {
+      *x += 1;
+    };
+    f();
+
+    fn mut_ref_arg(mut arg : &mut [u8]) -> &mut [u8] {
+        &mut arg[..] //~^ WARN: variable does not need to be mutable
+
+    }
+
+    let mut v : &mut Vec<()> = &mut vec![]; //~ WARN: variable does not need to be mutable
+
+    v.push(());
+
+    // positive cases
+    let mut a = 2;
+    a = 3;
+    let mut a = Vec::new();
+    a.push(3);
+    let mut a = Vec::new();
+    callback(|| {
+        a.push(3);
+    });
+    let mut a = Vec::new();
+    callback(|| {
+        callback(|| {
+            a.push(3);
+        });
+    });
+    let (mut a, b) = (1, 2);
+    a = 34;
+
+    match 30 {
+        mut x => {
+            x = 21;
+        }
+    }
+
+    match (30, 2) {
+      (mut x, 1) |
+      (mut x, 2) |
+      (mut x, 3) => {
+        x = 21
+      }
+      _ => {}
+    }
+
+    // Attribute should be respected on match arms
+    match 0 {
+        #[allow(unused_mut)]
+        mut x => {
+            let mut y = 1;
+        },
+    }
+
+    let x = |mut y: isize| y = 32;
+    fn nothing(mut foo: isize) { foo = 37; }
+
+    // leading underscore should avoid the warning, just like the
+    // unused variable lint.
+    let mut _allowed = 1;
+
+    let mut raw_address_of_mut = 1; // OK
+    let mut_ptr = &raw mut raw_address_of_mut;
+
+    let mut raw_address_of_const = 1; //~ WARN: variable does not need to be mutable
+    let const_ptr = &raw const raw_address_of_const;
+}
+
+fn callback<F>(f: F) where F: FnOnce() {}
+
+// make sure the lint attribute can be turned off
+#[allow(unused_mut)]
+fn foo(mut a: isize) {
+    let mut a = 3;
+    let mut b = vec![2];
+}
+
+// make sure the lint attribute can be turned off on let statements
+#[deny(unused_mut)]
+fn bar() {
+    #[allow(unused_mut)]
+    let mut a = 3;
+    let mut b = vec![2]; //~ ERROR: variable does not need to be mutable
+
+}