Rollup merge of #58267 - estebank:match-arms, r=matthewjasper

Tweak "incompatible match arms" error

- Point at the body expression of the match arm with the type error.
- Point at the prior match arms explicitly stating the evaluated type.
- Point at the entire match expr in a secondary span, instead of primary.
- For type errors in the first match arm, the cause is outside of the
  match, treat as implicit block error to give a more appropriate error.

Fix #46776, fix #57206.
CC #24157, #38234.

src/test/ui/if/if-let-arm-types.rs

@@ -1,10 +1,11 @@
 fn main() {
-    if let Some(b) = None { //~ ERROR: `if let` arms have incompatible types
-        //~^ expected (), found integer
-        //~| expected type `()`
-        //~| found type `{integer}`
+    if let Some(b) = None {
+        //~^ NOTE if let` arms have incompatible types
         ()
     } else {
         1
     };
+    //~^^ ERROR: `if let` arms have incompatible types
+    //~| NOTE expected (), found integer
+    //~| NOTE expected type `()`
 }

src/test/ui/if/if-let-arm-types.stderr

@@ -1,25 +1,17 @@
 error[E0308]: `if let` arms have incompatible types
-  --> $DIR/if-let-arm-types.rs:2:5
+  --> $DIR/if-let-arm-types.rs:6:9
    |
-LL | /     if let Some(b) = None { //~ ERROR: `if let` arms have incompatible types
-LL | |         //~^ expected (), found integer
-LL | |         //~| expected type `()`
-LL | |         //~| found type `{integer}`
-...  |
+LL | /     if let Some(b) = None {
+LL | |         //~^ NOTE if let` arms have incompatible types
+LL | |         ()
+LL | |     } else {
 LL | |         1
+   | |         ^ expected (), found integer
 LL | |     };
-   | |_____^ expected (), found integer
+   | |_____- `if let` arms have incompatible types
    |
    = note: expected type `()`
               found type `{integer}`
-note: `if let` arm with an incompatible type
-  --> $DIR/if-let-arm-types.rs:7:12
-   |
-LL |       } else {
-   |  ____________^
-LL | |         1
-LL | |     };
-   | |_____^
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-11319.rs

@@ -1,12 +1,14 @@
 fn main() {
     match Some(10) {
-    //~^ ERROR match arms have incompatible types
-    //~| expected type `bool`
-    //~| found type `()`
-    //~| expected bool, found ()
+    //~^ NOTE `match` arms have incompatible types
         Some(5) => false,
+        //~^ NOTE this is found to be of type `bool`
         Some(2) => true,
+        //~^ NOTE this is found to be of type `bool`
         None    => (),
+        //~^ ERROR match arms have incompatible types
+        //~| NOTE expected bool, found ()
+        //~| NOTE expected type `bool`
         _       => true
     }
 }

src/test/ui/issues/issue-11319.stderr

@@ -1,16 +1,20 @@
 error[E0308]: match arms have incompatible types
-  --> $DIR/issue-11319.rs:2:5
+  --> $DIR/issue-11319.rs:8:20
    |
 LL | /     match Some(10) {
-LL | |     //~^ ERROR match arms have incompatible types
-LL | |     //~| expected type `bool`
-LL | |     //~| found type `()`
-...  |
+LL | |     //~^ NOTE `match` arms have incompatible types
+LL | |         Some(5) => false,
+   | |                    ----- this is found to be of type `bool`
+LL | |         //~^ NOTE this is found to be of type `bool`
+LL | |         Some(2) => true,
+   | |                    ---- this is found to be of type `bool`
+LL | |         //~^ NOTE this is found to be of type `bool`
 LL | |         None    => (),
-   | |                    -- match arm with an incompatible type
+   | |                    ^^ expected bool, found ()
+...  |
 LL | |         _       => true
 LL | |     }
-   | |_____^ expected bool, found ()
+   | |_____- `match` arms have incompatible types
    |
    = note: expected type `bool`
               found type `()`

src/test/ui/issues/issue-17728.rs

@@ -97,7 +97,7 @@ impl Debug for Player {
 }
 
 fn str_to_direction(to_parse: &str) -> RoomDirection {
-    match to_parse { //~ ERROR match arms have incompatible types
+    match to_parse {
         "w" | "west" => RoomDirection::West,
         "e" | "east" => RoomDirection::East,
         "n" | "north" => RoomDirection::North,
@@ -108,6 +108,7 @@ fn str_to_direction(to_parse: &str) -> RoomDirection {
         "down" => RoomDirection::Down,
         _ => None
     }
+        //~^^ ERROR match arms have incompatible types
 }
 
 fn main() {

src/test/ui/issues/issue-17728.stderr

@@ -10,17 +10,19 @@ LL |             Some(entry) => Ok(entry),
    |                            ^^^^^^^^^ ...but data from `room` is returned here
 
 error[E0308]: match arms have incompatible types
-  --> $DIR/issue-17728.rs:100:5
+  --> $DIR/issue-17728.rs:109:14
    |
-LL | /     match to_parse { //~ ERROR match arms have incompatible types
+LL | /     match to_parse {
 LL | |         "w" | "west" => RoomDirection::West,
 LL | |         "e" | "east" => RoomDirection::East,
 LL | |         "n" | "north" => RoomDirection::North,
 ...  |
+LL | |         "down" => RoomDirection::Down,
+   | |                   ------------------- this and all prior arms are found to be of type `RoomDirection`
 LL | |         _ => None
-   | |              ---- match arm with an incompatible type
+   | |              ^^^^ expected enum `RoomDirection`, found enum `std::option::Option`
 LL | |     }
-   | |_____^ expected enum `RoomDirection`, found enum `std::option::Option`
+   | |_____- `match` arms have incompatible types
    |
    = note: expected type `RoomDirection`
               found type `std::option::Option<_>`

src/test/ui/issues/issue-24036.rs

@@ -6,11 +6,11 @@ fn closure_to_loc() {
 
 fn closure_from_match() {
     let x = match 1usize {
-    //~^ ERROR match arms have incompatible types
         1 => |c| c + 1,
         2 => |c| c - 1,
         _ => |c| c - 1
     };
+    //~^^^ ERROR match arms have incompatible types
 }
 
 fn main() { }

src/test/ui/issues/issue-24036.stderr

@@ -10,20 +10,20 @@ LL |     x = |c| c + 1;
    = help: consider boxing your closure and/or using it as a trait object
 
 error[E0308]: match arms have incompatible types
-  --> $DIR/issue-24036.rs:8:13
+  --> $DIR/issue-24036.rs:10:14
    |
 LL |       let x = match 1usize {
-   |  _____________^
-LL | |     //~^ ERROR match arms have incompatible types
+   |  _____________-
 LL | |         1 => |c| c + 1,
+   | |              --------- this is found to be of type `[closure@$DIR/issue-24036.rs:9:14: 9:23]`
 LL | |         2 => |c| c - 1,
-   | |              --------- match arm with an incompatible type
+   | |              ^^^^^^^^^ expected closure, found a different closure
 LL | |         _ => |c| c - 1
 LL | |     };
-   | |_____^ expected closure, found a different closure
+   | |_____- `match` arms have incompatible types
    |
-   = note: expected type `[closure@$DIR/issue-24036.rs:10:14: 10:23]`
-              found type `[closure@$DIR/issue-24036.rs:11:14: 11:23]`
+   = note: expected type `[closure@$DIR/issue-24036.rs:9:14: 9:23]`
+              found type `[closure@$DIR/issue-24036.rs:10:14: 10:23]`
    = note: no two closures, even if identical, have the same type
    = help: consider boxing your closure and/or using it as a trait object
 

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

@@ -0,0 +1,45 @@
+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
+}
+
+fn test_func3(n: i32) -> i32 {
+    let x = match n {
+    //~^ NOTE `match` arms have incompatible types
+        1 => 'b',
+        2 => 'b',
+        3 => 'b',
+        4 => 'b',
+        5 => 'b',
+        6 => 'b',
+        //~^ NOTE this and all prior arms are 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 +1,53 @@
+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[E0308]: match arms have incompatible types
+  --> $DIR/match-type-err-first-arm.rs:39:14
+   |
+LL |       let x = match n {
+   |  _____________-
+LL | |     //~^ NOTE `match` arms have incompatible types
+LL | |         1 => 'b',
+LL | |         2 => 'b',
+...  |
+LL | |         6 => 'b',
+   | |              --- this and all prior arms are found to be of type `char`
+LL | |         //~^ NOTE this and all prior arms are 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 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.