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go/types: implement term lists
This is a straightforward port of CL 339596 to go/types, differing only in the package declaration. Change-Id: If5bf8fd5667bee91b04fdb797702e6045d5fba7b Reviewed-on: https://go-review.googlesource.com/c/go/+/342330 Trust: Robert Findley <rfindley@google.com> Run-TryBot: Robert Findley <rfindley@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Findley
parent
3d679c6554
commit
94002f6fca
167
src/go/types/termlist.go
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167
src/go/types/termlist.go
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@ -0,0 +1,167 @@
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package types
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import "bytes"
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// A termlist represents the type set represented by the union
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// t1 ∪ y2 ∪ ... tn of the type sets of the terms t1 to tn.
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// A termlist is in normal form if all terms are disjoint.
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// termlist operations don't require the operands to be in
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// normal form.
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type termlist []*term
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// topTermList represents the set of all types.
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// It is in normal form.
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var topTermlist = termlist{new(term)}
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// String prints the termlist exactly (without normalization).
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func (xl termlist) String() string {
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if len(xl) == 0 {
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return "∅"
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}
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var buf bytes.Buffer
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for i, x := range xl {
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if i > 0 {
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buf.WriteString(" ∪ ")
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}
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buf.WriteString(x.String())
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}
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return buf.String()
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}
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// isEmpty reports whether the termlist xl represents the empty set of types.
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func (xl termlist) isEmpty() bool {
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// If there's a non-nil term, the entire list is not empty.
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// If the termlist is in normal form, this requires at most
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// one iteration.
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for _, x := range xl {
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if x != nil {
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return false
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}
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}
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return true
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}
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// isTop reports whether the termlist xl represents the set of all types.
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func (xl termlist) isTop() bool {
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// If there's a ⊤ (top) term, the entire list is ⊤ (top).
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// If the termlist is in normal form, this requires at most
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// one iteration.
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for _, x := range xl {
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if x != nil && x.typ == nil {
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return true
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}
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}
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return false
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}
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// norm returns the normal form of xl.
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func (xl termlist) norm() termlist {
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// Quadratic algorithm, but good enough for now.
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// TODO(gri) fix asymptotic performance
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used := make([]bool, len(xl))
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var rl termlist
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for i, xi := range xl {
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if xi == nil || used[i] {
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continue
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}
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for j := i + 1; j < len(xl); j++ {
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xj := xl[j]
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if xj == nil || used[j] {
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continue
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}
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if u1, u2 := xi.union(xj); u2 == nil {
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// If we encounter a ⊤ (top) term, the entire
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// list is ⊤ (top). Exit early.
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// (Note that this is not just an optimization;
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// if we continue, we may end up with a ⊤ term
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// and other terms and the result would not be
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// in normal form.)
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if u1.typ == nil {
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return topTermlist
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}
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xi = u1
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used[j] = true // xj is now unioned into xi - ignore it in future iterations
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}
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}
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rl = append(rl, xi)
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}
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return rl
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}
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// If the type set represented by xl is specified by a single (non-⊤) term,
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// structuralType returns that type. Otherwise it returns nil.
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func (xl termlist) structuralType() Type {
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if nl := xl.norm(); len(nl) == 1 {
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return nl[0].typ // if nl.isTop() then typ is nil, which is ok
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}
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return nil
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}
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// union returns the union xl ∪ yl.
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func (xl termlist) union(yl termlist) termlist {
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return append(xl, yl...).norm()
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}
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// intersect returns the intersection xl ∩ yl.
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func (xl termlist) intersect(yl termlist) termlist {
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if xl.isEmpty() || yl.isEmpty() {
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return nil
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}
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// Quadratic algorithm, but good enough for now.
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// TODO(gri) fix asymptotic performance
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var rl termlist
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for _, x := range xl {
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for _, y := range yl {
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if r := x.intersect(y); r != nil {
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rl = append(rl, r)
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}
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}
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}
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return rl.norm()
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}
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// equal reports whether xl and yl represent the same type set.
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func (xl termlist) equal(yl termlist) bool {
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// TODO(gri) this should be more efficient
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return xl.subsetOf(yl) && yl.subsetOf(xl)
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}
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// includes reports whether t ∈ xl.
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func (xl termlist) includes(t Type) bool {
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for _, x := range xl {
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if x.includes(t) {
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return true
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}
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}
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return false
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}
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// supersetOf reports whether y ⊆ xl.
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func (xl termlist) supersetOf(y *term) bool {
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for _, x := range xl {
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if y.subsetOf(x) {
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return true
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}
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}
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return false
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}
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// subsetOf reports whether xl ⊆ yl.
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func (xl termlist) subsetOf(yl termlist) bool {
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if yl.isEmpty() {
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return xl.isEmpty()
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}
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// each term x of xl must be a subset of yl
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for _, x := range xl {
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if !yl.supersetOf(x) {
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return false // x is not a subset yl
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}
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}
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return true
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}
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278
src/go/types/termlist_test.go
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278
src/go/types/termlist_test.go
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@ -0,0 +1,278 @@
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package types
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import (
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"strings"
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"testing"
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)
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// maketl makes a term list from a string of the term list.
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func maketl(s string) termlist {
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s = strings.Replace(s, " ", "", -1)
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names := strings.Split(s, "∪")
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r := make(termlist, len(names))
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for i, n := range names {
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r[i] = testTerm(n)
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}
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return r
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}
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func TestTermlistTop(t *testing.T) {
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if !topTermlist.isTop() {
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t.Errorf("topTermlist is not top")
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}
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}
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func TestTermlistString(t *testing.T) {
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for _, want := range []string{
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"∅",
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"⊤",
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"int",
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"~int",
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"∅ ∪ ∅",
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"⊤ ∪ ⊤",
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"∅ ∪ ⊤ ∪ int",
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} {
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if got := maketl(want).String(); got != want {
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t.Errorf("(%v).String() == %v", want, got)
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}
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}
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}
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func TestTermlistIsEmpty(t *testing.T) {
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for test, want := range map[string]bool{
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"∅": true,
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"∅ ∪ ∅": true,
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"∅ ∪ ∅ ∪ ⊤": false,
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"⊤": false,
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"⊤ ∪ int": false,
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} {
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xl := maketl(test)
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got := xl.isEmpty()
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if got != want {
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t.Errorf("(%v).isEmpty() == %v; want %v", test, got, want)
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}
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}
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}
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func TestTermlistIsTop(t *testing.T) {
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for test, want := range map[string]bool{
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"∅": false,
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"∅ ∪ ∅": false,
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"int ∪ ~string": false,
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"∅ ∪ ∅ ∪ ⊤": true,
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"⊤": true,
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"⊤ ∪ int": true,
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} {
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xl := maketl(test)
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got := xl.isTop()
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if got != want {
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t.Errorf("(%v).isTop() == %v; want %v", test, got, want)
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}
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}
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}
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func TestTermlistNorm(t *testing.T) {
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for _, test := range []struct {
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xl, want string
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}{
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{"∅", "∅"},
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{"∅ ∪ ∅", "∅"},
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{"∅ ∪ int", "int"},
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{"⊤ ∪ int", "⊤"},
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{"~int ∪ int", "~int"},
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{"int ∪ ~string ∪ int", "int ∪ ~string"},
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{"~int ∪ string ∪ ⊤ ∪ ~string ∪ int", "⊤"},
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} {
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xl := maketl(test.xl)
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got := maketl(test.xl).norm()
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if got.String() != test.want {
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t.Errorf("(%v).norm() = %v; want %v", xl, got, test.want)
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}
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}
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}
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func TestTermlistStructuralType(t *testing.T) {
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// helper to deal with nil types
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tstring := func(typ Type) string {
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if typ == nil {
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return "nil"
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}
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return typ.String()
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}
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for test, want := range map[string]string{
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"∅": "nil",
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"⊤": "nil",
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"int": "int",
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"~int": "int",
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"~int ∪ string": "nil",
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"∅ ∪ int": "int",
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"∅ ∪ ~int": "int",
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"∅ ∪ ~int ∪ string": "nil",
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} {
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xl := maketl(test)
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got := tstring(xl.structuralType())
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if got != want {
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t.Errorf("(%v).structuralType() == %v; want %v", test, got, want)
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}
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}
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}
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func TestTermlistUnion(t *testing.T) {
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for _, test := range []struct {
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xl, yl, want string
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}{
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{"∅", "∅", "∅"},
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{"∅", "⊤", "⊤"},
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{"∅", "int", "int"},
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{"⊤", "~int", "⊤"},
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{"int", "~int", "~int"},
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{"int", "string", "int ∪ string"},
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{"int ∪ string", "~string", "int ∪ ~string"},
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{"~int ∪ string", "~string ∪ int", "~int ∪ ~string"},
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{"~int ∪ string ∪ ∅", "~string ∪ int", "~int ∪ ~string"},
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{"~int ∪ string ∪ ⊤", "~string ∪ int", "⊤"},
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} {
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xl := maketl(test.xl)
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yl := maketl(test.yl)
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got := xl.union(yl).String()
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if got != test.want {
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t.Errorf("(%v).union(%v) = %v; want %v", test.xl, test.yl, got, test.want)
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}
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}
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}
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func TestTermlistIntersect(t *testing.T) {
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for _, test := range []struct {
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xl, yl, want string
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}{
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{"∅", "∅", "∅"},
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{"∅", "⊤", "∅"},
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{"∅", "int", "∅"},
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{"⊤", "~int", "~int"},
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{"int", "~int", "int"},
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{"int", "string", "∅"},
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{"int ∪ string", "~string", "string"},
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{"~int ∪ string", "~string ∪ int", "int ∪ string"},
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{"~int ∪ string ∪ ∅", "~string ∪ int", "int ∪ string"},
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{"~int ∪ string ∪ ⊤", "~string ∪ int", "int ∪ ~string"},
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} {
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xl := maketl(test.xl)
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yl := maketl(test.yl)
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got := xl.intersect(yl).String()
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if got != test.want {
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t.Errorf("(%v).intersect(%v) = %v; want %v", test.xl, test.yl, got, test.want)
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}
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}
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}
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func TestTermlistEqual(t *testing.T) {
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for _, test := range []struct {
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xl, yl string
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want bool
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}{
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{"∅", "∅", true},
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{"∅", "⊤", false},
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{"⊤", "⊤", true},
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{"⊤ ∪ int", "⊤", true},
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{"⊤ ∪ int", "string ∪ ⊤", true},
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{"int ∪ ~string", "string ∪ int", false},
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{"int ∪ ~string ∪ ∅", "string ∪ int ∪ ~string", true},
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} {
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xl := maketl(test.xl)
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yl := maketl(test.yl)
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got := xl.equal(yl)
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if got != test.want {
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t.Errorf("(%v).equal(%v) = %v; want %v", test.xl, test.yl, got, test.want)
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}
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}
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}
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func TestTermlistIncludes(t *testing.T) {
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for _, test := range []struct {
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xl, typ string
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want bool
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}{
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{"∅", "int", false},
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{"⊤", "int", true},
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{"~int", "int", true},
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{"int", "string", false},
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{"~int", "string", false},
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{"int ∪ string", "string", true},
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{"~int ∪ string", "int", true},
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{"~int ∪ string ∪ ∅", "string", true},
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{"~string ∪ ∅ ∪ ⊤", "int", true},
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} {
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xl := maketl(test.xl)
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yl := testTerm(test.typ).typ
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got := xl.includes(yl)
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if got != test.want {
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t.Errorf("(%v).includes(%v) = %v; want %v", test.xl, yl, got, test.want)
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}
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}
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}
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func TestTermlistSupersetOf(t *testing.T) {
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for _, test := range []struct {
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xl, typ string
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want bool
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}{
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{"∅", "∅", true},
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{"∅", "⊤", false},
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{"∅", "int", false},
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{"⊤", "∅", true},
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{"⊤", "⊤", true},
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{"⊤", "int", true},
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{"⊤", "~int", true},
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{"~int", "int", true},
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{"~int", "~int", true},
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{"int", "~int", false},
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{"int", "string", false},
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{"~int", "string", false},
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{"int ∪ string", "string", true},
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{"int ∪ string", "~string", false},
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{"~int ∪ string", "int", true},
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{"~int ∪ string ∪ ∅", "string", true},
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{"~string ∪ ∅ ∪ ⊤", "int", true},
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} {
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xl := maketl(test.xl)
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y := testTerm(test.typ)
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got := xl.supersetOf(y)
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if got != test.want {
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t.Errorf("(%v).supersetOf(%v) = %v; want %v", test.xl, y, got, test.want)
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}
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}
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}
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func TestTermlistSubsetOf(t *testing.T) {
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for _, test := range []struct {
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xl, yl string
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want bool
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}{
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{"∅", "∅", true},
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{"∅", "⊤", true},
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{"⊤", "∅", false},
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{"⊤", "⊤", true},
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{"int", "int ∪ string", true},
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{"~int", "int ∪ string", false},
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{"~int", "string ∪ string ∪ int ∪ ~int", true},
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{"int ∪ string", "string", false},
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{"int ∪ string", "string ∪ int", true},
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{"int ∪ ~string", "string ∪ int", false},
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{"int ∪ ~string", "string ∪ int ∪ ⊤", true},
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{"int ∪ ~string", "string ∪ int ∪ ∅ ∪ string", false},
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} {
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xl := maketl(test.xl)
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yl := maketl(test.yl)
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got := xl.subsetOf(yl)
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if got != test.want {
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t.Errorf("(%v).subsetOf(%v) = %v; want %v", test.xl, test.yl, got, test.want)
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}
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}
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}
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