Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0004.md b/compiler/rustc_error_codes/src/error_codes/E0004.md
new file mode 100644
index 000000000..b79ef5fd8
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0004.md
@@ -0,0 +1,46 @@
+This error indicates that the compiler cannot guarantee a matching pattern for
+one or more possible inputs to a match expression. Guaranteed matches are
+required in order to assign values to match expressions, or alternatively,
+determine the flow of execution.
+
+Erroneous code example:
+
+```compile_fail,E0004
+enum Terminator {
+    HastaLaVistaBaby,
+    TalkToMyHand,
+}
+
+let x = Terminator::HastaLaVistaBaby;
+
+match x { // error: non-exhaustive patterns: `HastaLaVistaBaby` not covered
+    Terminator::TalkToMyHand => {}
+}
+```
+
+If you encounter this error you must alter your patterns so that every possible
+value of the input type is matched. For types with a small number of variants
+(like enums) you should probably cover all cases explicitly. Alternatively, the
+underscore `_` wildcard pattern can be added after all other patterns to match
+"anything else". Example:
+
+```
+enum Terminator {
+    HastaLaVistaBaby,
+    TalkToMyHand,
+}
+
+let x = Terminator::HastaLaVistaBaby;
+
+match x {
+    Terminator::TalkToMyHand => {}
+    Terminator::HastaLaVistaBaby => {}
+}
+
+// or:
+
+match x {
+    Terminator::TalkToMyHand => {}
+    _ => {}
+}
+```