enum-variant-generic-args-pats-pass: harden + describe.

Author: Centril

src/test/ui/type-alias-enum-variants/enum-variant-generic-args-pats-pass.rs

@@ -1,15 +1,23 @@
 // run-pass
 
+// Check that resolving, in the value namespace, to an `enum` variant
+// through a type alias is well behaved in the presence of generics.
+// We check for situations with:
+// 1. a generic type `Alias<T>`, we can type-apply `Alias` when referring to a variant.
+// 2. a monotype `AliasFixed` of generic `Enum<T>`, we can refer to variants
+//    and the type-application of `T` in `AliasFixed` is kept.
+
 #![allow(irrefutable_let_patterns)]
 
 #[allow(dead_code)]
-enum Enum<T> { TSVariant(T), SVariant { v: T } }
+enum Enum<T> { TSVariant(T), SVariant { v: T }, UVariant }
 type Alias<T> = Enum<T>;
 type AliasFixed = Enum<()>;
 
 macro_rules! is_variant {
     (TSVariant, $expr:expr) => (is_variant!(@check TSVariant, (_), $expr));
     (SVariant, $expr:expr) => (is_variant!(@check SVariant, { v: _ }, $expr));
+    (UVariant, $expr:expr) => (is_variant!(@check UVariant, {}, $expr));
     (@check $variant:ident, $matcher:tt, $expr:expr) => (
         assert!(if let Enum::$variant::<()> $matcher = $expr { true } else { false },
                 "expr does not have correct type");
@@ -38,4 +46,15 @@ fn main() {
     is_variant!(SVariant, Alias::<()>::SVariant { v: () });
 
     is_variant!(SVariant, AliasFixed::SVariant { v: () });
+
+    // Unit variant
+
+    is_variant!(UVariant, Enum::UVariant);
+    is_variant!(UVariant, Enum::UVariant::<()>);
+    is_variant!(UVariant, Enum::<()>::UVariant);
+
+    is_variant!(UVariant, Alias::UVariant);
+    is_variant!(UVariant, Alias::<()>::UVariant);
+
+    is_variant!(UVariant, AliasFixed::UVariant);
 }