u = Typ[Invalid]
			}
		} else {
			terms = append(terms, term)
			u = &Union{terms}
		}

		if i > 0 {
			check.recordTypeAndValue(blist[i-1], typexpr, u, nil)
		}
	}

	if !isValid(u) {
		return u
	}

	// Check validity of terms.
	// Do this check later because it requires types to be set up.

				u = Typ[Invalid]
			}
		} else {
			terms = append(terms, term)
			u = &Union{terms}
		}

		if i > 0 {
			check.recordTypeAndValue(blist[i-1], typexpr, u, nil)
		}
	}

	if !isValid(u) {
		return u
	}

	// Check validity of terms.
	// Do this check later because it requires types to be set up.

			check.dump("%v: %s (type %s) is typed", atPos(x), x, info.typ)
			panic("unreachable")
		}
		check.recordTypeAndValue(x, info.mode, info.typ, info.val)
	}
}

func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
	assert(x != nil)
	assert(typ != nil)
	if mode == invalid {
		return // omit
	}
	if mode == constant_ {
		assert(val != nil)

			check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
			panic("unreachable")
		}
		check.recordTypeAndValue(x, info.mode, info.typ, info.val)
	}
}

func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
	assert(x != nil)
	assert(typ != nil)
	if mode == invalid {
		return // omit
	}
	if mode == constant_ {
		assert(val != nil)

	typ := check.typInternal(e, def)
	assert(isTyped(typ))
	if isGeneric(typ) {
		check.errorf(e, WrongTypeArgCount, "cannot use generic type %s without instantiation", typ)
		typ = Typ[Invalid]
	}
	check.recordTypeAndValue(e, typexpr, typ, nil)
	return typ
}

// genericType is like typ but the type must be an (uninstantiated) generic
// type. If cause is non-nil and the type expression was a valid type but not

	typ := check.typInternal(e, def)
	assert(isTyped(typ))
	if isGeneric(typ) {
		check.errorf(e, WrongTypeArgCount, "cannot use generic type %s without instantiation", typ)
		typ = Typ[Invalid]
	}
	check.recordTypeAndValue(e, typexpr, typ, nil)
	return typ
}

// genericType is like typ but the type must be an (uninstantiated) generic
// type. If cause is non-nil and the type expression was a valid type but not

	// Since we type-checked T rather than ...T, we also need to retro-actively
	// record the type for ...T.
	if variadic {
		last := params[len(params)-1]
		last.typ = &Slice{elem: last.typ}
		check.recordTypeAndValue(list.List[len(list.List)-1].Type, typexpr, last.typ, nil)
	}

	return

	// Since we type-checked T rather than ...T, we also need to retro-actively
	// record the type for ...T.
	if variadic {
		last := params[len(params)-1]
		last.typ = &Slice{elem: last.typ}
		check.recordTypeAndValue(list[len(list)-1].Type, typexpr, last.typ, nil)
	}

	return

		c := operand{old.mode, x, old.typ, old.val, 0}
		check.convertUntyped(&c, typ)
		if c.mode == invalid {
			return
		}
	}

	// Everything's fine, record final type and value for x.
	check.recordTypeAndValue(x, old.mode, typ, old.val)
}

// updateExprVal updates the value of x to val.
func (check *Checker) updateExprVal(x ast.Expr, val constant.Value) {
	if info, ok := check.untyped[x]; ok {
		info.val = val

		c := operand{old.mode, x, old.typ, old.val, 0}
		check.convertUntyped(&c, typ)
		if c.mode == invalid {
			return
		}
	}

	// Everything's fine, record final type and value for x.
	check.recordTypeAndValue(x, old.mode, typ, old.val)
}

// updateExprVal updates the value of x to val.
func (check *Checker) updateExprVal(x syntax.Expr, val constant.Value) {
	if info, ok := check.untyped[x]; ok {
		info.val = val