Add ui tests for manual_arithmetic_check

Author: GuillaumeGomez

tests/ui/manual_arithmetic_check-2.rs

@@ -0,0 +1,17 @@
+//@no-rustfix
+#![warn(clippy::manual_arithmetic_check)]
+
+fn main() {
+    let a = 12;
+    let b = 13;
+
+    let result = if a > b { b - a } else { 0 };
+    //~^ ERROR: reverted arithmetic check before subtraction
+    let result = if b < a { b - a } else { 0 };
+    //~^ ERROR: reverted arithmetic check before subtraction
+
+    let result = if a > b { 0 } else { a - b };
+    //~^ ERROR: reverted arithmetic check before subtraction
+    let result = if b < a { 0 } else { a - b };
+    //~^ ERROR: reverted arithmetic check before subtraction
+}

tests/ui/manual_arithmetic_check-2.stderr

@@ -0,0 +1,72 @@
+error: reverted arithmetic check before subtraction
+  --> tests/ui/manual_arithmetic_check-2.rs:8:21
+   |
+LL |     let result = if a > b { b - a } else { 0 };
+   |                     ^^^^^   ----- help: try replacing it with: `a - b`
+   |
+note: you check that `a` is bigger than `b`
+  --> tests/ui/manual_arithmetic_check-2.rs:8:21
+   |
+LL |     let result = if a > b { b - a } else { 0 };
+   |                     ^^^^^
+note: but then you subtract `a` from `b`
+  --> tests/ui/manual_arithmetic_check-2.rs:8:29
+   |
+LL |     let result = if a > b { b - a } else { 0 };
+   |                             ^^^^^
+   = note: `-D clippy::manual-arithmetic-check` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::manual_arithmetic_check)]`
+
+error: reverted arithmetic check before subtraction
+  --> tests/ui/manual_arithmetic_check-2.rs:10:21
+   |
+LL |     let result = if b < a { b - a } else { 0 };
+   |                     ^^^^^   ----- help: try replacing it with: `a - b`
+   |
+note: you check that `a` is bigger than `b`
+  --> tests/ui/manual_arithmetic_check-2.rs:10:21
+   |
+LL |     let result = if b < a { b - a } else { 0 };
+   |                     ^^^^^
+note: but then you subtract `a` from `b`
+  --> tests/ui/manual_arithmetic_check-2.rs:10:29
+   |
+LL |     let result = if b < a { b - a } else { 0 };
+   |                             ^^^^^
+
+error: reverted arithmetic check before subtraction
+  --> tests/ui/manual_arithmetic_check-2.rs:13:21
+   |
+LL |     let result = if a > b { 0 } else { a - b };
+   |                     ^^^^^              ----- help: try replacing it with: `b - a`
+   |
+note: you check that `b` is bigger than `a`
+  --> tests/ui/manual_arithmetic_check-2.rs:13:21
+   |
+LL |     let result = if a > b { 0 } else { a - b };
+   |                     ^^^^^
+note: but then you subtract `b` from `a`
+  --> tests/ui/manual_arithmetic_check-2.rs:13:40
+   |
+LL |     let result = if a > b { 0 } else { a - b };
+   |                                        ^^^^^
+
+error: reverted arithmetic check before subtraction
+  --> tests/ui/manual_arithmetic_check-2.rs:15:21
+   |
+LL |     let result = if b < a { 0 } else { a - b };
+   |                     ^^^^^              ----- help: try replacing it with: `b - a`
+   |
+note: you check that `b` is bigger than `a`
+  --> tests/ui/manual_arithmetic_check-2.rs:15:21
+   |
+LL |     let result = if b < a { 0 } else { a - b };
+   |                     ^^^^^
+note: but then you subtract `b` from `a`
+  --> tests/ui/manual_arithmetic_check-2.rs:15:40
+   |
+LL |     let result = if b < a { 0 } else { a - b };
+   |                                        ^^^^^
+
+error: aborting due to 4 previous errors
+

tests/ui/manual_arithmetic_check.fixed

@@ -0,0 +1,16 @@
+#![warn(clippy::manual_arithmetic_check)]
+
+fn main() {
+    let a = 12u32;
+    let b = 13u32;
+
+    let result = a.saturating_sub(b);
+    //~^ ERROR: manual arithmetic check found
+    let result = a.saturating_sub(b);
+    //~^ ERROR: manual arithmetic check found
+
+    let result = a.saturating_sub(b);
+    //~^ ERROR: manual arithmetic check found
+    let result = a.saturating_sub(b);
+    //~^ ERROR: manual arithmetic check found
+}

tests/ui/manual_arithmetic_check.rs

@@ -0,0 +1,16 @@
+#![warn(clippy::manual_arithmetic_check)]
+
+fn main() {
+    let a = 12u32;
+    let b = 13u32;
+
+    let result = if a > b { a - b } else { 0 };
+    //~^ ERROR: manual arithmetic check found
+    let result = if b < a { a - b } else { 0 };
+    //~^ ERROR: manual arithmetic check found
+
+    let result = if a < b { 0 } else { a - b };
+    //~^ ERROR: manual arithmetic check found
+    let result = if b > a { 0 } else { a - b };
+    //~^ ERROR: manual arithmetic check found
+}

tests/ui/manual_arithmetic_check.stderr

@@ -0,0 +1,29 @@
+error: manual arithmetic check found
+  --> tests/ui/manual_arithmetic_check.rs:7:18
+   |
+LL |     let result = if a > b { a - b } else { 0 };
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `a.saturating_sub(b)`
+   |
+   = note: `-D clippy::manual-arithmetic-check` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::manual_arithmetic_check)]`
+
+error: manual arithmetic check found
+  --> tests/ui/manual_arithmetic_check.rs:9:18
+   |
+LL |     let result = if b < a { a - b } else { 0 };
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `a.saturating_sub(b)`
+
+error: manual arithmetic check found
+  --> tests/ui/manual_arithmetic_check.rs:12:18
+   |
+LL |     let result = if a < b { 0 } else { a - b };
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `a.saturating_sub(b)`
+
+error: manual arithmetic check found
+  --> tests/ui/manual_arithmetic_check.rs:14:18
+   |
+LL |     let result = if b > a { 0 } else { a - b };
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `a.saturating_sub(b)`
+
+error: aborting due to 4 previous errors
+