ASTTRef.java

import java.util.Set;

public class ASTTRef implements ASTType {

    private final ASTType type;

    public ASTTRef(ASTType _type) {
        this.type = _type;
    }
    
    public ASTType getType() {
        return type;
    }

    @Override
    public String toStr() {
        return "ref("+type.toStr()+")";
    }

    @Override
    public boolean eqt(ASTType t) {
        if (!(t instanceof ASTTRef other))
            return false;
        return type.eqt(other.getType());
    }

    @Override
    public boolean subtypeOf(ASTType t, Environment<ASTType> e, Set<String> seen) throws InterpreterError {
        t = ASTTypeDef.unfold(t, e);
        if (!(t instanceof ASTTRef other))
            return false;
        
        ASTType thisInner = ASTTypeDef.unfold(this.type, e);
        ASTType otherInner = ASTTypeDef.unfold(other.getType(), e);
        
        // A<:>B
        return thisInner.subtypeOf(otherInner, e, seen) && otherInner.subtypeOf(thisInner, e, seen);
    }

}