allow non-exhaustive enums with no fields

Author: Vexu

src/analyze.cpp

@@ -2560,8 +2560,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
 
     assert(!enum_type->data.enumeration.fields);
     uint32_t field_count = (uint32_t)decl_node->data.container_decl.fields.length;
-    if (field_count == 0 || (field_count == 1 &&
-        buf_eql_str(decl_node->data.container_decl.fields.at(0)->data.struct_field.name, "_"))) {
+    if (field_count == 0) {
         add_node_error(g, decl_node, buf_sprintf("enums must have 1 or more fields"));
 
         enum_type->data.enumeration.src_field_count = field_count;
@@ -2657,7 +2656,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
                 add_node_error(g, field_node, buf_sprintf("non-exhaustive enum must specify size"));
                 enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
             }
-            if (log2_u64(field_count - 1) == enum_type->size_in_bits) {
+            if (field_count > 1 && log2_u64(field_count - 1) == enum_type->size_in_bits) {
                 add_node_error(g, field_node, buf_sprintf("non-exhaustive enum specifies every value"));
                 enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
             }