test: fix interfaces

Author: MilesCranmer

src/Interfaces.jl

@@ -70,8 +70,8 @@ function _check_get_metadata(ex::AbstractExpression)
     new_ex = with_metadata(ex, get_metadata(ex))
     return new_ex == ex && new_ex isa typeof(ex)
 end
-function _check_get_tree(ex::AbstractExpression{T,N}) where {T,N}
-    return get_tree(ex) isa N || get_tree(ex) isa AbstractReadOnlyNode{T,N}
+function _check_get_tree(ex::AbstractExpression{T,N}) where {T,D,N<:AbstractExpressionNode{T,D}}
+    return get_tree(ex) isa N || get_tree(ex) isa AbstractReadOnlyNode{T,D,N}
 end
 function _check_get_operators(ex::AbstractExpression)
     return get_operators(ex) isa AbstractOperatorEnum