public SubstMap unify(final Loc loc, final Type other, final TypeEnv env) {
if (env.checkVisited(this, other)) return SubstMap.EMPTY;
if (other instanceof TypeVar) return SubstMap.bindVar(loc, (TypeVar) other, this);
// if our application expression can be evaluated, unify against that.
if (isAbsApply()) return eval().unify(loc, other, env);
final Type otherEval = other.deref().eval();
if (otherEval instanceof TypeApp) {
final TypeApp otherApp = (TypeApp) otherEval;
final SubstMap baseSubst = base.unify(loc, otherApp.base, env);
if (baseSubst != null) {
final SubstMap argSubst =
arg.subst(baseSubst).unify(loc, otherApp.arg.subst(baseSubst), env);
if (argSubst != null) return baseSubst.compose(loc, argSubst);
}
} else if (kind.equals(otherEval.getKind())) {
// other is not an application expression, but kinds match.
// other type classes do opportunistic matching of type apps
// implementations of unify. This approach is really ad-hoc,
// needs to be rationalized.
return otherEval.unify(loc, this, env);
}
return null;
}
/** internal reality checks on param/arg kinds */
private boolean checkKindAgreement(final Type abs, final Type argDeref) {
final Kind absKind = abs.getKind();
if (!(absKind instanceof ArrowKind)) {
Session.error(
loc,
"internal error: abs {0} has non-lambda kind {1} in type app {2}",
abs.dump(),
absKind.dump(),
dump());
return false;
}
final Kind paramKind = ((ArrowKind) absKind).getParamKind();
final Kind argKind = argDeref.getKind();
if (!paramKind.equals(argKind)) {
Session.error(
loc,
"internal error: param kind {0} incompatible with arg kind {1} in type app {2}",
paramKind.dump(),
argKind.dump(),
dump());
return false;
}
return true;
}
@Override
public boolean equals(final Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
if (!super.equals(o)) return false;
final TypeParam typeParam = (TypeParam) o;
if (kind != null ? !kind.equals(typeParam.kind) : typeParam.kind != null) return false;
if (typeScope != null ? typeScope != typeParam.typeScope : typeParam.typeScope != null)
return false;
return true;
}
@Override
public int hashCode() {
int result = super.hashCode();
result = 31 * result + (kind != null ? kind.hashCode() : 0);
return result;
}
