Sema: fix generic fn instantiation with anytype

When the anytype parameter had only one-possible-value
(e.g. `void`), it would create a mismatch in the function type and the
function call. Now the function type and the callsite both omit the
one-possible-value anytype parameter in instantiated generic functions.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index c8b905f23f..29cad45f9a 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -6158,6 +6158,9 @@ fn zirParamAnytype(
             // function type of the function instruction in this block.
             return;
         }
+        if (null != try sema.typeHasOnePossibleValue(block, src, param_ty)) {
+            return;
+        }
         // The map is already populated but we do need to add a runtime parameter.
         try block.params.append(sema.gpa, .{
             .ty = param_ty,