Add test for type mismatch on first match arm

Author: estebank

src/test/ui/match/match-type-err-first-arm.rs

@@ -0,0 +1,27 @@
+fn main() {
+    let _ = test_func1(1);
+    let _ = test_func2(1);
+}
+
+fn test_func1(n: i32) -> i32 {
+    //~^ NOTE expected `i32` because of return type
+    match n {
+        12 => 'b',
+        //~^ ERROR mismatched types
+        //~| NOTE expected i32, found char
+        _ => 42,
+    }
+}
+
+fn test_func2(n: i32) -> i32 {
+    let x = match n {
+    //~^ NOTE `match` arms have incompatible types
+        12 => 'b',
+        //~^ NOTE this is found to be of type `char`
+        _ => 42,
+        //~^ ERROR match arms have incompatible types
+        //~| NOTE expected char, found integer
+        //~| NOTE expected type `char`
+    };
+    x
+}

src/test/ui/match/match-type-err-first-arm.stderr

@@ -0,0 +1,31 @@
+error[E0308]: mismatched types
+  --> $DIR/match-type-err-first-arm.rs:9:15
+   |
+LL | fn test_func1(n: i32) -> i32 {
+   |                          --- expected `i32` because of return type
+...
+LL |         12 => 'b',
+   |               ^^^ expected i32, found char
+
+error[E0308]: match arms have incompatible types
+  --> $DIR/match-type-err-first-arm.rs:21:14
+   |
+LL |       let x = match n {
+   |  _____________-
+LL | |     //~^ NOTE `match` arms have incompatible types
+LL | |         12 => 'b',
+   | |               --- this is found to be of type `char`
+LL | |         //~^ NOTE this is found to be of type `char`
+LL | |         _ => 42,
+   | |              ^^ expected char, found integer
+...  |
+LL | |         //~| NOTE expected type `char`
+LL | |     };
+   | |_____- `match` arms have incompatible types
+   |
+   = note: expected type `char`
+              found type `{integer}`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.