Fix exhaustiveness in case a byte string literal is used at slice type

src/test/ui/match/type_polymorphic_byte_str_literals.rs

@@ -0,0 +1,36 @@
+#[deny(unreachable_patterns)]
+
+fn parse_data1(data: &[u8]) -> u32 {
+    match data {
+        b"" => 1,
+        _ => 2,
+    }
+}
+
+fn parse_data2(data: &[u8]) -> u32 {
+    match data { //~ ERROR non-exhaustive patterns: `&[_, ..]` not covered
+        b"" => 1,
+    }
+}
+
+fn parse_data3(data: &[u8; 0]) -> u8 {
+    match data {
+        b"" => 1,
+    }
+}
+
+fn parse_data4(data: &[u8]) -> u8 {
+    match data { //~ ERROR non-exhaustive patterns
+        b"aaa" => 0,
+        [_, _, _] => 1,
+    }
+}
+
+fn parse_data5(data: &[u8; 3]) -> u8 {
+    match data {
+        b"aaa" => 0,
+        [_, _, _] => 1,
+    }
+}
+
+fn main() {}

src/test/ui/match/type_polymorphic_byte_str_literals.stderr

@@ -0,0 +1,21 @@
+error[E0004]: non-exhaustive patterns: `&[_, ..]` not covered
+  --> $DIR/type_polymorphic_byte_str_literals.rs:11:11
+   |
+LL |     match data {
+   |           ^^^^ pattern `&[_, ..]` not covered
+   |
+   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
+   = note: the matched value is of type `&[u8]`
+
+error[E0004]: non-exhaustive patterns: `&[]`, `&[_]`, `&[_, _]` and 1 more not covered
+  --> $DIR/type_polymorphic_byte_str_literals.rs:23:11
+   |
+LL |     match data {
+   |           ^^^^ patterns `&[]`, `&[_]`, `&[_, _]` and 1 more not covered
+   |
+   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
+   = note: the matched value is of type `&[u8]`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0004`.

src/test/ui/pattern/usefulness/match-byte-array-patterns-2.stderr

@@ -7,11 +7,11 @@ LL |     match buf {
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
    = note: the matched value is of type `&[u8; 4]`
 
-error[E0004]: non-exhaustive patterns: `&[0_u8..=64_u8, _, _, _]` and `&[66_u8..=u8::MAX, _, _, _]` not covered
+error[E0004]: non-exhaustive patterns: `&[]`, `&[_]`, `&[_, _]` and 2 more not covered
   --> $DIR/match-byte-array-patterns-2.rs:10:11
    |
 LL |     match buf {
-   |           ^^^ patterns `&[0_u8..=64_u8, _, _, _]` and `&[66_u8..=u8::MAX, _, _, _]` not covered
+   |           ^^^ patterns `&[]`, `&[_]`, `&[_, _]` and 2 more not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
    = note: the matched value is of type `&[u8]`