Handle empty matches cleanly

src/test/ui/pattern/usefulness/match-empty.rs

@@ -44,22 +44,20 @@ macro_rules! match_false {
 fn foo(x: Foo) {
     match x {} // ok
     match x {
-        _ => {}, // Not detected as unreachable, see #55123.
+        _ => {}, //~ ERROR unreachable pattern
     }
     match x {
-    //~^ ERROR non-exhaustive patterns: `_` not covered
-        _ if false => {}, // Not detected as unreachable nor exhaustive.
+        _ if false => {}, //~ ERROR unreachable pattern
     }
 }
 
 fn never(x: !) {
     match x {} // ok
     match x {
-        _ => {}, // Not detected as unreachable.
+        _ => {}, //~ ERROR unreachable pattern
     }
     match x {
-    //~^ ERROR non-exhaustive patterns: `_` not covered
-        _ if false => {}, // Not detected as unreachable nor exhaustive.
+        _ if false => {}, //~ ERROR unreachable pattern
     }
 }
 

src/test/ui/pattern/usefulness/match-empty.stderr

@@ -1,26 +1,35 @@
-error[E0004]: non-exhaustive patterns: `_` not covered
-  --> $DIR/match-empty.rs:49:11
+error: unreachable pattern
+  --> $DIR/match-empty.rs:47:9
    |
-LL | enum Foo {}
-   | ----------- `Foo` defined here
-...
-LL |     match x {
-   |           ^ pattern `_` not covered
+LL |         _ => {},
+   |         ^
    |
-   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `Foo`
+note: the lint level is defined here
+  --> $DIR/match-empty.rs:3:9
+   |
+LL | #![deny(unreachable_patterns)]
+   |         ^^^^^^^^^^^^^^^^^^^^
 
-error[E0004]: non-exhaustive patterns: `_` not covered
-  --> $DIR/match-empty.rs:60:11
+error: unreachable pattern
+  --> $DIR/match-empty.rs:50:9
    |
-LL |     match x {
-   |           ^ pattern `_` not covered
+LL |         _ if false => {},
+   |         ^
+
+error: unreachable pattern
+  --> $DIR/match-empty.rs:57:9
    |
-   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `!`
+LL |         _ => {},
+   |         ^
+
+error: unreachable pattern
+  --> $DIR/match-empty.rs:60:9
+   |
+LL |         _ if false => {},
+   |         ^
 
 error[E0004]: non-exhaustive patterns: type `u8` is non-empty
-  --> $DIR/match-empty.rs:77:18
+  --> $DIR/match-empty.rs:75:18
    |
 LL |     match_empty!(0u8);
    |                  ^^^
@@ -29,7 +38,7 @@ LL |     match_empty!(0u8);
    = note: the matched value is of type `u8`
 
 error[E0004]: non-exhaustive patterns: type `NonEmptyStruct` is non-empty
-  --> $DIR/match-empty.rs:79:18
+  --> $DIR/match-empty.rs:77:18
    |
 LL | struct NonEmptyStruct(bool);
    | ---------------------------- `NonEmptyStruct` defined here
@@ -41,7 +50,7 @@ LL |     match_empty!(NonEmptyStruct(true));
    = note: the matched value is of type `NonEmptyStruct`
 
 error[E0004]: non-exhaustive patterns: type `NonEmptyUnion1` is non-empty
-  --> $DIR/match-empty.rs:81:18
+  --> $DIR/match-empty.rs:79:18
    |
 LL | / union NonEmptyUnion1 {
 LL | |     foo: (),
@@ -55,7 +64,7 @@ LL |       match_empty!((NonEmptyUnion1 { foo: () }));
    = note: the matched value is of type `NonEmptyUnion1`
 
 error[E0004]: non-exhaustive patterns: type `NonEmptyUnion2` is non-empty
-  --> $DIR/match-empty.rs:83:18
+  --> $DIR/match-empty.rs:81:18
    |
 LL | / union NonEmptyUnion2 {
 LL | |     foo: (),
@@ -70,7 +79,7 @@ LL |       match_empty!((NonEmptyUnion2 { foo: () }));
    = note: the matched value is of type `NonEmptyUnion2`
 
 error[E0004]: non-exhaustive patterns: `Foo(_)` not covered
-  --> $DIR/match-empty.rs:85:18
+  --> $DIR/match-empty.rs:83:18
    |
 LL | / enum NonEmptyEnum1 {
 LL | |     Foo(bool),
@@ -87,7 +96,7 @@ LL |       match_empty!(NonEmptyEnum1::Foo(true));
    = note: the matched value is of type `NonEmptyEnum1`
 
 error[E0004]: non-exhaustive patterns: `Foo(_)` and `Bar` not covered
-  --> $DIR/match-empty.rs:87:18
+  --> $DIR/match-empty.rs:85:18
    |
 LL | / enum NonEmptyEnum2 {
 LL | |     Foo(bool),
@@ -108,7 +117,7 @@ LL |       match_empty!(NonEmptyEnum2::Foo(true));
    = note: the matched value is of type `NonEmptyEnum2`
 
 error[E0004]: non-exhaustive patterns: `V1`, `V2`, `V3` and 2 more not covered
-  --> $DIR/match-empty.rs:89:18
+  --> $DIR/match-empty.rs:87:18
    |
 LL | / enum NonEmptyEnum5 {
 LL | |     V1, V2, V3, V4, V5,
@@ -122,7 +131,7 @@ LL |       match_empty!(NonEmptyEnum5::V1);
    = note: the matched value is of type `NonEmptyEnum5`
 
 error[E0004]: non-exhaustive patterns: `_` not covered
-  --> $DIR/match-empty.rs:92:18
+  --> $DIR/match-empty.rs:90:18
    |
 LL |     match_false!(0u8);
    |                  ^^^ pattern `_` not covered
@@ -131,7 +140,7 @@ LL |     match_false!(0u8);
    = note: the matched value is of type `u8`
 
 error[E0004]: non-exhaustive patterns: `NonEmptyStruct(_)` not covered
-  --> $DIR/match-empty.rs:94:18
+  --> $DIR/match-empty.rs:92:18
    |
 LL | struct NonEmptyStruct(bool);
    | ---------------------------- `NonEmptyStruct` defined here
@@ -143,7 +152,7 @@ LL |     match_false!(NonEmptyStruct(true));
    = note: the matched value is of type `NonEmptyStruct`
 
 error[E0004]: non-exhaustive patterns: `NonEmptyUnion1 { .. }` not covered
-  --> $DIR/match-empty.rs:96:18
+  --> $DIR/match-empty.rs:94:18
    |
 LL | / union NonEmptyUnion1 {
 LL | |     foo: (),
@@ -157,7 +166,7 @@ LL |       match_false!((NonEmptyUnion1 { foo: () }));
    = note: the matched value is of type `NonEmptyUnion1`
 
 error[E0004]: non-exhaustive patterns: `NonEmptyUnion2 { .. }` not covered
-  --> $DIR/match-empty.rs:98:18
+  --> $DIR/match-empty.rs:96:18
    |
 LL | / union NonEmptyUnion2 {
 LL | |     foo: (),
@@ -172,7 +181,7 @@ LL |       match_false!((NonEmptyUnion2 { foo: () }));
    = note: the matched value is of type `NonEmptyUnion2`
 
 error[E0004]: non-exhaustive patterns: `Foo(_)` not covered
-  --> $DIR/match-empty.rs:100:18
+  --> $DIR/match-empty.rs:98:18
    |
 LL | / enum NonEmptyEnum1 {
 LL | |     Foo(bool),
@@ -189,7 +198,7 @@ LL |       match_false!(NonEmptyEnum1::Foo(true));
    = note: the matched value is of type `NonEmptyEnum1`
 
 error[E0004]: non-exhaustive patterns: `Foo(_)` and `Bar` not covered
-  --> $DIR/match-empty.rs:102:18
+  --> $DIR/match-empty.rs:100:18
    |
 LL | / enum NonEmptyEnum2 {
 LL | |     Foo(bool),
@@ -210,7 +219,7 @@ LL |       match_false!(NonEmptyEnum2::Foo(true));
    = note: the matched value is of type `NonEmptyEnum2`
 
 error[E0004]: non-exhaustive patterns: `V1`, `V2`, `V3` and 2 more not covered
-  --> $DIR/match-empty.rs:104:18
+  --> $DIR/match-empty.rs:102:18
    |
 LL | / enum NonEmptyEnum5 {
 LL | |     V1, V2, V3, V4, V5,
@@ -223,6 +232,6 @@ LL |       match_false!(NonEmptyEnum5::V1);
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
    = note: the matched value is of type `NonEmptyEnum5`
 
-error: aborting due to 16 previous errors
+error: aborting due to 18 previous errors
 
 For more information about this error, try `rustc --explain E0004`.

src/test/ui/rfc-2008-non-exhaustive/enum_same_crate_empty_match.rs

@@ -25,7 +25,7 @@ pub enum EmptyNonExhaustiveEnum {}
 fn empty_non_exhaustive(x: EmptyNonExhaustiveEnum) {
     match x {}
     match x {
-        _ => {} // not detected as unreachable
+        _ => {}, //~ ERROR unreachable pattern
     }
 }
 

src/test/ui/rfc-2008-non-exhaustive/enum_same_crate_empty_match.stderr

@@ -1,3 +1,15 @@
+error: unreachable pattern
+  --> $DIR/enum_same_crate_empty_match.rs:28:9
+   |
+LL |         _ => {},
+   |         ^
+   |
+note: the lint level is defined here
+  --> $DIR/enum_same_crate_empty_match.rs:1:9
+   |
+LL | #![deny(unreachable_patterns)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+
 error[E0004]: non-exhaustive patterns: `Unit`, `Tuple(_)` and `Struct { .. }` not covered
   --> $DIR/enum_same_crate_empty_match.rs:33:11
    |
@@ -42,6 +54,6 @@ LL |       match NormalEnum::Unit {}
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
    = note: the matched value is of type `NormalEnum`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0004`.