GlobalVarExpression

        pub const GlobalVarExpression = struct {
            pub const ops = [_]AbbrevOp{
                .{ .literal = @backingInt(ModuleBlock.MetadataBlock.Code.GLOBAL_VAR_EXPR) },
                .{ .literal = 0 }, // is distinct
                MetadataAbbrev, // variable
                MetadataAbbrev, // expression
            };

            variable: Builder.Metadata.Optional,
            expression: Builder.Metadata.Optional,
        }