3 files changed, 157 insertions, 3 deletions

diff --git a/tests/ui/identity_op.fixed b/tests/ui/identity_op.fixed
index b18d8560f6f..2e8e2366de6 100644
--- a/tests/ui/identity_op.fixed
+++ b/tests/ui/identity_op.fixed
@@ -116,7 +116,7 @@ fn main() {
     //~^ ERROR: this operation has no effect
     (match a { 0 => 10, _ => 20 }) + if b { 3 } else { 4 };
     //~^ ERROR: this operation has no effect
-    (if b { 1 } else { 2 });
+    ((if b { 1 } else { 2 }));
     //~^ ERROR: this operation has no effect
 
     ({ a }) + 3;
@@ -212,3 +212,47 @@ fn issue_12050() {
         //~^ ERROR: this operation has no effect
     }
 }
+
+fn issue_13470() {
+    let x = 1i32;
+    let y = 1i32;
+    // Removes the + 0i32 while keeping the parentheses around x + y so the cast operation works
+    let _: u64 = (x + y) as u64;
+    //~^ ERROR: this operation has no effect
+    // both of the next two lines should look the same after rustfix
+    let _: u64 = 1u64 & (x + y) as u64;
+    //~^ ERROR: this operation has no effect
+    // Same as above, but with extra redundant parenthesis
+    let _: u64 = 1u64 & ((x + y)) as u64;
+    //~^ ERROR: this operation has no effect
+    // Should maintain parenthesis even if the surrounding expr has the same precedence
+    let _: u64 = 5u64 + ((x + y)) as u64;
+    //~^ ERROR: this operation has no effect
+
+    // If we don't maintain the parens here, the behavior changes
+    let _ = -(x + y);
+    //~^ ERROR: this operation has no effect
+    // Similarly, we need to maintain parens here
+    let _ = -(x / y);
+    //~^ ERROR: this operation has no effect
+    // Maintain parenthesis if the parent expr is of higher precedence
+    let _ = 2i32 * (x + y);
+    //~^ ERROR: this operation has no effect
+    // Maintain parenthesis if the parent expr is the same precedence
+    // as not all operations are associative
+    let _ = 2i32 - (x - y);
+    //~^ ERROR: this operation has no effect
+    // But make sure that inner parens still exist
+    let z = 1i32;
+    let _ = 2 + (x + (y * z));
+    //~^ ERROR: this operation has no effect
+    // Maintain parenthesis if the parent expr is of lower precedence
+    // This is for clarity, and clippy will not warn on these being unnecessary
+    let _ = 2i32 + (x * y);
+    //~^ ERROR: this operation has no effect
+
+    let x = 1i16;
+    let y = 1i16;
+    let _: u64 = 1u64 + ((x as i32 + y as i32) as u64);
+    //~^ ERROR: this operation has no effect
+}
diff --git a/tests/ui/identity_op.rs b/tests/ui/identity_op.rs
index f1f01b42447..3e20fa6f2b8 100644
--- a/tests/ui/identity_op.rs
+++ b/tests/ui/identity_op.rs
@@ -212,3 +212,47 @@ fn issue_12050() {
         //~^ ERROR: this operation has no effect
     }
 }
+
+fn issue_13470() {
+    let x = 1i32;
+    let y = 1i32;
+    // Removes the + 0i32 while keeping the parentheses around x + y so the cast operation works
+    let _: u64 = (x + y + 0i32) as u64;
+    //~^ ERROR: this operation has no effect
+    // both of the next two lines should look the same after rustfix
+    let _: u64 = 1u64 & (x + y + 0i32) as u64;
+    //~^ ERROR: this operation has no effect
+    // Same as above, but with extra redundant parenthesis
+    let _: u64 = 1u64 & ((x + y) + 0i32) as u64;
+    //~^ ERROR: this operation has no effect
+    // Should maintain parenthesis even if the surrounding expr has the same precedence
+    let _: u64 = 5u64 + ((x + y) + 0i32) as u64;
+    //~^ ERROR: this operation has no effect
+
+    // If we don't maintain the parens here, the behavior changes
+    let _ = -(x + y + 0i32);
+    //~^ ERROR: this operation has no effect
+    // Similarly, we need to maintain parens here
+    let _ = -(x / y / 1i32);
+    //~^ ERROR: this operation has no effect
+    // Maintain parenthesis if the parent expr is of higher precedence
+    let _ = 2i32 * (x + y + 0i32);
+    //~^ ERROR: this operation has no effect
+    // Maintain parenthesis if the parent expr is the same precedence
+    // as not all operations are associative
+    let _ = 2i32 - (x - y - 0i32);
+    //~^ ERROR: this operation has no effect
+    // But make sure that inner parens still exist
+    let z = 1i32;
+    let _ = 2 + (x + (y * z) + 0);
+    //~^ ERROR: this operation has no effect
+    // Maintain parenthesis if the parent expr is of lower precedence
+    // This is for clarity, and clippy will not warn on these being unnecessary
+    let _ = 2i32 + (x * y * 1i32);
+    //~^ ERROR: this operation has no effect
+
+    let x = 1i16;
+    let y = 1i16;
+    let _: u64 = 1u64 + ((x as i32 + y as i32) as u64 + 0u64);
+    //~^ ERROR: this operation has no effect
+}
diff --git a/tests/ui/identity_op.stderr b/tests/ui/identity_op.stderr
index 9fff86b86f9..99a58ef2c1b 100644
--- a/tests/ui/identity_op.stderr
+++ b/tests/ui/identity_op.stderr
@@ -149,7 +149,7 @@ error: this operation has no effect
   --> tests/ui/identity_op.rs:119:5
    |
 LL |     (if b { 1 } else { 2 }) + 0;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `(if b { 1 } else { 2 })`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((if b { 1 } else { 2 }))`
 
 error: this operation has no effect
   --> tests/ui/identity_op.rs:122:5
@@ -313,5 +313,71 @@ error: this operation has no effect
 LL |         let _: i32 = **&&*&x + 0;
    |                      ^^^^^^^^^^^ help: consider reducing it to: `***&&*&x`
 
-error: aborting due to 52 previous errors
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:220:18
+   |
+LL |     let _: u64 = (x + y + 0i32) as u64;
+   |                  ^^^^^^^^^^^^^^ help: consider reducing it to: `(x + y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:223:25
+   |
+LL |     let _: u64 = 1u64 & (x + y + 0i32) as u64;
+   |                         ^^^^^^^^^^^^^^ help: consider reducing it to: `(x + y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:226:25
+   |
+LL |     let _: u64 = 1u64 & ((x + y) + 0i32) as u64;
+   |                         ^^^^^^^^^^^^^^^^ help: consider reducing it to: `((x + y))`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:229:25
+   |
+LL |     let _: u64 = 5u64 + ((x + y) + 0i32) as u64;
+   |                         ^^^^^^^^^^^^^^^^ help: consider reducing it to: `((x + y))`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:233:14
+   |
+LL |     let _ = -(x + y + 0i32);
+   |              ^^^^^^^^^^^^^^ help: consider reducing it to: `(x + y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:236:14
+   |
+LL |     let _ = -(x / y / 1i32);
+   |              ^^^^^^^^^^^^^^ help: consider reducing it to: `(x / y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:239:20
+   |
+LL |     let _ = 2i32 * (x + y + 0i32);
+   |                    ^^^^^^^^^^^^^^ help: consider reducing it to: `(x + y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:243:20
+   |
+LL |     let _ = 2i32 - (x - y - 0i32);
+   |                    ^^^^^^^^^^^^^^ help: consider reducing it to: `(x - y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:247:17
+   |
+LL |     let _ = 2 + (x + (y * z) + 0);
+   |                 ^^^^^^^^^^^^^^^^^ help: consider reducing it to: `(x + (y * z))`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:251:20
+   |
+LL |     let _ = 2i32 + (x * y * 1i32);
+   |                    ^^^^^^^^^^^^^^ help: consider reducing it to: `(x * y)`
+
+error: this operation has no effect
+  --> tests/ui/identity_op.rs:256:25
+   |
+LL |     let _: u64 = 1u64 + ((x as i32 + y as i32) as u64 + 0u64);
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider reducing it to: `((x as i32 + y as i32) as u64)`
+
+error: aborting due to 63 previous errors