func (subst *subster) typOrNil(typ Type) Type {
	if typ == nil {
		return Typ[Invalid]
	}
	return subst.typ(typ)
}

func (subst *subster) var_(v *Var) *Var {
	if v != nil {
		if typ := subst.typ(v.typ); typ != v.typ {
			return substVar(v, typ)
		}
	}
	return v
}

func substVar(v *Var, typ Type) *Var {
	copy := *v
	copy.typ = typ

func (subst *subster) typOrNil(typ Type) Type {
	if typ == nil {
		return Typ[Invalid]
	}
	return subst.typ(typ)
}

func (subst *subster) var_(v *Var) *Var {
	if v != nil {
		if typ := subst.typ(v.typ); typ != v.typ {
			return substVar(v, typ)
		}
	}
	return v
}

func substVar(v *Var, typ Type) *Var {
	copy := *v
	copy.typ = typ

		// hold the instantiated receiver.
		copy := *origSig
		sig = &copy
	}

	var rtyp Type
	if origm.hasPtrRecv() {
		rtyp = NewPointer(t)
	} else {
		rtyp = t
	}

	sig.recv = substVar(origSig.recv, rtyp)
	return substFunc(origm, sig)
}

// SetUnderlying sets the underlying type and marks t as complete.
// t must not have type arguments.
func (t *Named) SetUnderlying(underlying Type) {

		// hold the instantiated receiver.
		copy := *origSig
		sig = &copy
	}

	var rtyp Type
	if origm.hasPtrRecv() {
		rtyp = NewPointer(t)
	} else {
		rtyp = t
	}

	sig.recv = substVar(origSig.recv, rtyp)
	return substFunc(origm, sig)
}

// SetUnderlying sets the underlying type and marks t as complete.
// t must not have type arguments.
func (t *Named) SetUnderlying(underlying Type) {

// Count counts the number of non-overlapping instances of substr in s.
// If substr is an empty string, Count returns 1 + the number of Unicode code points in s.
func Count(s, substr string) int {
	// special case
	if len(substr) == 0 {
		return utf8.RuneCountInString(s) + 1
	}
	if len(substr) == 1 {
		return bytealg.CountString(s, substr[0])
	}
	n := 0
	for {
		i := Index(s, substr)
		if i == -1 {
			return n
		}
		n++

    result = dot_h_fname.substr(pos + sizeof("/bin/") - 1);
  } else {
    pos = dot_h_fname.find("/genfiles/");
    if (pos != string::npos) {
      result = dot_h_fname.substr(pos + sizeof("/genfiles/") - 1);
    }
  }
  if (result.size() > sizeof("external/") &&
      result.compare(0, sizeof("external/") - 1, "external/") == 0) {
    result = result.substr(sizeof("external/") - 1);
    pos = result.find('/');

		$sysname =~ s/([a-z])([A-Z])/${1}_$2/g;	# turn FooBar into Foo_Bar
		$sysname =~ y/a-z/A-Z/;
		if($libc) {
			$sysname =~ y/A-Z/a-z/;
			$sysname = substr $sysname, 4;
			$funcname = "libc_$sysname";
		}
	}
	if($libc) {
		if($funcname eq "") {
			$sysname = substr $sysname, 4;
			$sysname =~ y/A-Z/a-z/;
			$funcname = "libc_$sysname";
		}
		$sysname = "abi.FuncPCABI0(${funcname}_trampoline)";
	}

  int idx_arrow = einsum_equation.find("->");
  StringRef calc_eq = einsum_equation.substr(0, idx_arrow);
  StringRef out_eq = einsum_equation.substr(idx_arrow + 2);

  int idx_comma = calc_eq.find(',');
  StringRef lhs_eq = calc_eq.substr(0, idx_comma);
  StringRef rhs_eq = calc_eq.substr(idx_comma + 1);

  std::string target_eq;
  if (is_lhs) {
    target_eq = lhs_eq;

  }

  // Parse equation.
  int idx_arrow = equation.find("->");
  StringRef calc_eq = equation.substr(0, idx_arrow);
  StringRef out_eq = equation.substr(idx_arrow + 2);

  int idx_comma = calc_eq.find(',');
  StringRef lhs_eq = calc_eq.substr(0, idx_comma);
  StringRef rhs_eq = calc_eq.substr(idx_comma + 1);

  if (absl::StrContains(rhs_eq, ",")) return false;

  int lhs_out_idx_start = out_eq.size();

                         data_types_str, "'"));
      }
      inside_subtype = false;
    }
    if (inside_subtype) continue;
    if (c == ',') {
      dtypes.push_back(
          std::string(data_types_str.substr(cur_pos, i - cur_pos)));
      cur_pos = i + 1;
    }
  }
  if (inside_subtype) {
    return errors::FailedPrecondition(
        absl::StrCat("Syntax error: expected a ')' in input data types '",