Fix suggestions for redundant_pattern_matching

Fixes the problem displayed in rust-lang#4344 (comment).

We now append `{}` to the suggestion so that the conditional has the
correct syntax again.

(If we were to _remove_ the `if` instead, it would trigger the
`unused_must_use` warning for `#[must_use]` types.

clippy_lints/src/redundant_pattern_matching.rs

@@ -90,7 +90,7 @@ fn find_sugg_for_if_let<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr,
                 db.span_suggestion(
                     span,
                     "try this",
-                    format!("if {}.{}", snippet(cx, op.span, "_"), good_method),
+                    format!("if {}.{} {{}}", snippet(cx, op.span, "_"), good_method),
                     Applicability::MachineApplicable, // snippet
                 );
             },
@@ -153,7 +153,7 @@ fn find_sugg_for_match<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr, o
                     db.span_suggestion(
                         span,
                         "try this",
-                        format!("{}.{}", snippet(cx, op.span, "_"), good_method),
+                        format!("if {}.{} {{}}", snippet(cx, op.span, "_"), good_method),
                         Applicability::MachineApplicable, // snippet
                     );
                 },

tests/ui/redundant_pattern_matching.fixed

@@ -0,0 +1,41 @@
+// run-rustfix
+
+#![warn(clippy::all)]
+#![warn(clippy::redundant_pattern_matching)]
+
+fn main() {
+    if Ok::<i32, i32>(42).is_ok() {}
+
+    if Err::<i32, i32>(42).is_err() {}
+
+    if None::<()>.is_none() {}
+
+    if Some(42).is_some() {}
+
+    if Ok::<i32, i32>(42).is_ok() {}
+
+    if Err::<i32, i32>(42).is_err() {}
+
+    if None::<i32>.is_none() {}
+
+    if Some(42).is_some() {}
+
+    if let Ok(x) = Ok::<i32, i32>(42) {
+        println!("{}", x);
+    }
+
+    if Ok::<i32, i32>(42).is_ok() {};
+
+    if Ok::<i32, i32>(42).is_err() {};
+
+    if Err::<i32, i32>(42).is_err() {};
+
+    if Err::<i32, i32>(42).is_ok() {};
+
+    if Some(42).is_some() {};
+
+    if None::<()>.is_none() {};
+
+    let bla: Result<usize, ()> = Ok(4);
+    if bla.is_ok() {};
+}

tests/ui/redundant_pattern_matching.rs

@@ -1,3 +1,5 @@
+// run-rustfix
+
 #![warn(clippy::all)]
 #![warn(clippy::redundant_pattern_matching)]
 
@@ -51,4 +53,11 @@ fn main() {
         Some(_) => false,
         None => true,
     };
+
+    let bla: Result<usize, ()> = Ok(4);
+    if let Ok(_) = bla {
+        true
+    } else {
+        false
+    };
 }

tests/ui/redundant_pattern_matching.stderr

@@ -1,82 +1,93 @@
 error: redundant pattern matching, consider using `is_ok()`
-  --> $DIR/redundant_pattern_matching.rs:5:12
+  --> $DIR/redundant_pattern_matching.rs:7:12
    |
 LL |     if let Ok(_) = Ok::<i32, i32>(42) {}
-   |     -------^^^^^------------------------ help: try this: `if Ok::<i32, i32>(42).is_ok()`
+   |     -------^^^^^------------------------ help: try this: `if Ok::<i32, i32>(42).is_ok() {}`
    |
    = note: `-D clippy::redundant-pattern-matching` implied by `-D warnings`
 
 error: redundant pattern matching, consider using `is_err()`
-  --> $DIR/redundant_pattern_matching.rs:7:12
+  --> $DIR/redundant_pattern_matching.rs:9:12
    |
 LL |     if let Err(_) = Err::<i32, i32>(42) {}
-   |     -------^^^^^^------------------------- help: try this: `if Err::<i32, i32>(42).is_err()`
+   |     -------^^^^^^------------------------- help: try this: `if Err::<i32, i32>(42).is_err() {}`
 
 error: redundant pattern matching, consider using `is_none()`
-  --> $DIR/redundant_pattern_matching.rs:9:12
+  --> $DIR/redundant_pattern_matching.rs:11:12
    |
 LL |     if let None = None::<()> {}
-   |     -------^^^^---------------- help: try this: `if None::<()>.is_none()`
+   |     -------^^^^---------------- help: try this: `if None::<()>.is_none() {}`
 
 error: redundant pattern matching, consider using `is_some()`
-  --> $DIR/redundant_pattern_matching.rs:11:12
+  --> $DIR/redundant_pattern_matching.rs:13:12
    |
 LL |     if let Some(_) = Some(42) {}
-   |     -------^^^^^^^-------------- help: try this: `if Some(42).is_some()`
+   |     -------^^^^^^^-------------- help: try this: `if Some(42).is_some() {}`
 
 error: redundant pattern matching, consider using `is_ok()`
-  --> $DIR/redundant_pattern_matching.rs:25:5
+  --> $DIR/redundant_pattern_matching.rs:27:5
    |
 LL | /     match Ok::<i32, i32>(42) {
 LL | |         Ok(_) => true,
 LL | |         Err(_) => false,
 LL | |     };
-   | |_____^ help: try this: `Ok::<i32, i32>(42).is_ok()`
+   | |_____^ help: try this: `if Ok::<i32, i32>(42).is_ok() {}`
 
 error: redundant pattern matching, consider using `is_err()`
-  --> $DIR/redundant_pattern_matching.rs:30:5
+  --> $DIR/redundant_pattern_matching.rs:32:5
    |
 LL | /     match Ok::<i32, i32>(42) {
 LL | |         Ok(_) => false,
 LL | |         Err(_) => true,
 LL | |     };
-   | |_____^ help: try this: `Ok::<i32, i32>(42).is_err()`
+   | |_____^ help: try this: `if Ok::<i32, i32>(42).is_err() {}`
 
 error: redundant pattern matching, consider using `is_err()`
-  --> $DIR/redundant_pattern_matching.rs:35:5
+  --> $DIR/redundant_pattern_matching.rs:37:5
    |
 LL | /     match Err::<i32, i32>(42) {
 LL | |         Ok(_) => false,
 LL | |         Err(_) => true,
 LL | |     };
-   | |_____^ help: try this: `Err::<i32, i32>(42).is_err()`
+   | |_____^ help: try this: `if Err::<i32, i32>(42).is_err() {}`
 
 error: redundant pattern matching, consider using `is_ok()`
-  --> $DIR/redundant_pattern_matching.rs:40:5
+  --> $DIR/redundant_pattern_matching.rs:42:5
    |
 LL | /     match Err::<i32, i32>(42) {
 LL | |         Ok(_) => true,
 LL | |         Err(_) => false,
 LL | |     };
-   | |_____^ help: try this: `Err::<i32, i32>(42).is_ok()`
+   | |_____^ help: try this: `if Err::<i32, i32>(42).is_ok() {}`
 
 error: redundant pattern matching, consider using `is_some()`
-  --> $DIR/redundant_pattern_matching.rs:45:5
+  --> $DIR/redundant_pattern_matching.rs:47:5
    |
 LL | /     match Some(42) {
 LL | |         Some(_) => true,
 LL | |         None => false,
 LL | |     };
-   | |_____^ help: try this: `Some(42).is_some()`
+   | |_____^ help: try this: `if Some(42).is_some() {}`
 
 error: redundant pattern matching, consider using `is_none()`
-  --> $DIR/redundant_pattern_matching.rs:50:5
+  --> $DIR/redundant_pattern_matching.rs:52:5
    |
 LL | /     match None::<()> {
 LL | |         Some(_) => false,
 LL | |         None => true,
 LL | |     };
-   | |_____^ help: try this: `None::<()>.is_none()`
+   | |_____^ help: try this: `if None::<()>.is_none() {}`
+
+error: redundant pattern matching, consider using `is_ok()`
+  --> $DIR/redundant_pattern_matching.rs:58:12
+   |
+LL |       if let Ok(_) = bla {
+   |  _____-      ^^^^^
+LL | |         true
+LL | |     } else {
+LL | |         false
+LL | |     };
+   | |_____- help: try this: `if bla.is_ok() {}`
 
-error: aborting due to 10 previous errors
+error: aborting due to 11 previous errors