Making try_err machine applicable

Author: jfrikker

clippy_lints/src/try_err.rs

@@ -80,7 +80,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TryErr {
                     "returning an `Err(_)` with the `?` operator",
                     "try this",
                     suggestion,
-                    Applicability::MaybeIncorrect
+                    Applicability::MachineApplicable
                 );
             }
         }

tests/ui/try_err.fixed

@@ -0,0 +1,75 @@
+// run-rustfix
+
+#![deny(clippy::try_err)]
+
+// Tests that a simple case works
+// Should flag `Err(err)?`
+pub fn basic_test() -> Result<i32, i32> {
+    let err: i32 = 1;
+    if true { // To avoid warnings during rustfix
+        return Err(err);
+    }
+    Ok(0)
+}
+
+// Tests that `.into()` is added when appropriate
+pub fn into_test() -> Result<i32, i32> {
+    let err: u8 = 1;
+    if true { // To avoid warnings during rustfix
+        return Err(err.into());
+    }
+    Ok(0)
+}
+
+// Tests that tries in general don't trigger the error
+pub fn negative_test() -> Result<i32, i32> {
+    Ok(nested_error()? + 1)
+}
+
+
+// Tests that `.into()` isn't added when the error type
+// matches the surrounding closure's return type, even
+// when it doesn't match the surrounding function's.
+pub fn closure_matches_test() -> Result<i32, i32> {
+    let res: Result<i32, i8> = Some(1).into_iter()
+        .map(|i| {
+            let err: i8 = 1;
+            if true { // To avoid warnings during rustfix
+                return Err(err);
+            }
+            Ok(i)
+        })
+        .next()
+        .unwrap();
+
+    Ok(res?)
+}
+
+// Tests that `.into()` isn't added when the error type
+// doesn't match the surrounding closure's return type.
+pub fn closure_into_test() -> Result<i32, i32> {
+    let res: Result<i32, i16> = Some(1).into_iter()
+        .map(|i| {
+            let err: i8 = 1;
+            if true { // To avoid warnings during rustfix
+                return Err(err.into());
+            }
+            Ok(i)
+        })
+        .next()
+        .unwrap();
+
+    Ok(res?)
+}
+
+fn nested_error() -> Result<i32, i32> {
+    Ok(1)
+}
+
+fn main() {
+    basic_test().unwrap();
+    into_test().unwrap();
+    negative_test().unwrap();
+    closure_matches_test().unwrap();
+    closure_into_test().unwrap();
+}

tests/ui/try_err.rs

@@ -1,17 +1,23 @@
+// run-rustfix
+
 #![deny(clippy::try_err)]
 
 // Tests that a simple case works
 // Should flag `Err(err)?`
 pub fn basic_test() -> Result<i32, i32> {
     let err: i32 = 1;
-    Err(err)?;
+    if true { // To avoid warnings during rustfix
+        Err(err)?;
+    }
     Ok(0)
 }
 
 // Tests that `.into()` is added when appropriate
 pub fn into_test() -> Result<i32, i32> {
     let err: u8 = 1;
-    Err(err)?;
+    if true { // To avoid warnings during rustfix
+        Err(err)?;
+    }
     Ok(0)
 }
 
@@ -28,7 +34,9 @@ pub fn closure_matches_test() -> Result<i32, i32> {
     let res: Result<i32, i8> = Some(1).into_iter()
         .map(|i| {
             let err: i8 = 1;
-            Err(err)?;
+            if true { // To avoid warnings during rustfix
+                Err(err)?;
+            }
             Ok(i)
         })
         .next()
@@ -43,7 +51,9 @@ pub fn closure_into_test() -> Result<i32, i32> {
     let res: Result<i32, i16> = Some(1).into_iter()
         .map(|i| {
             let err: i8 = 1;
-            Err(err)?;
+            if true { // To avoid warnings during rustfix
+                Err(err)?;
+            }
             Ok(i)
         })
         .next()

tests/ui/try_err.stderr

@@ -1,32 +1,32 @@
 error: returning an `Err(_)` with the `?` operator
-  --> $DIR/try_err.rs:7:5
+  --> $DIR/try_err.rs:10:9
    |
-LL |     Err(err)?;
-   |     ^^^^^^^^^ help: try this: `return Err(err)`
+LL |         Err(err)?;
+   |         ^^^^^^^^^ help: try this: `return Err(err)`
    |
 note: lint level defined here
-  --> $DIR/try_err.rs:1:9
+  --> $DIR/try_err.rs:3:9
    |
 LL | #![deny(clippy::try_err)]
    |         ^^^^^^^^^^^^^^^
 
 error: returning an `Err(_)` with the `?` operator
-  --> $DIR/try_err.rs:14:5
+  --> $DIR/try_err.rs:19:9
    |
-LL |     Err(err)?;
-   |     ^^^^^^^^^ help: try this: `return Err(err.into())`
+LL |         Err(err)?;
+   |         ^^^^^^^^^ help: try this: `return Err(err.into())`
 
 error: returning an `Err(_)` with the `?` operator
-  --> $DIR/try_err.rs:31:13
+  --> $DIR/try_err.rs:38:17
    |
-LL |             Err(err)?;
-   |             ^^^^^^^^^ help: try this: `return Err(err)`
+LL |                 Err(err)?;
+   |                 ^^^^^^^^^ help: try this: `return Err(err)`
 
 error: returning an `Err(_)` with the `?` operator
-  --> $DIR/try_err.rs:46:13
+  --> $DIR/try_err.rs:55:17
    |
-LL |             Err(err)?;
-   |             ^^^^^^^^^ help: try this: `return Err(err.into())`
+LL |                 Err(err)?;
+   |                 ^^^^^^^^^ help: try this: `return Err(err.into())`
 
 error: aborting due to 4 previous errors