| 1 | // Copyright 2021 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // Code generated by copytermlist.go DO NOT EDIT. |
| 6 | |
| 7 | package typeparams |
| 8 | |
| 9 | import "go/types" |
| 10 | |
| 11 | // A term describes elementary type sets: |
| 12 | // |
| 13 | // β : (*term)(nil) == β // set of no types (empty set) |
| 14 | // π€: &term{} == π€ // set of all types (π€niverse) |
| 15 | // T: &term{false, T} == {T} // set of type T |
| 16 | // ~t: &term{true, t} == {t' | under(t') == t} // set of types with underlying type t |
| 17 | // |
| 18 | type term struct { |
| 19 | tilde bool // valid if typ != nil |
| 20 | typ types.Type |
| 21 | } |
| 22 | |
| 23 | func (x *term) String() string { |
| 24 | switch { |
| 25 | case x == nil: |
| 26 | return "β " |
| 27 | case x.typ == nil: |
| 28 | return "π€" |
| 29 | case x.tilde: |
| 30 | return "~" + x.typ.String() |
| 31 | default: |
| 32 | return x.typ.String() |
| 33 | } |
| 34 | } |
| 35 | |
| 36 | // equal reports whether x and y represent the same type set. |
| 37 | func (x *term) equal(y *term) bool { |
| 38 | // easy cases |
| 39 | switch { |
| 40 | case x == nil || y == nil: |
| 41 | return x == y |
| 42 | case x.typ == nil || y.typ == nil: |
| 43 | return x.typ == y.typ |
| 44 | } |
| 45 | // β β x, y β π€ |
| 46 | |
| 47 | return x.tilde == y.tilde && types.Identical(x.typ, y.typ) |
| 48 | } |
| 49 | |
| 50 | // union returns the union x βͺ y: zero, one, or two non-nil terms. |
| 51 | func (x *term) union(y *term) (_, _ *term) { |
| 52 | // easy cases |
| 53 | switch { |
| 54 | case x == nil && y == nil: |
| 55 | return nil, nil // β βͺ β == β |
| 56 | case x == nil: |
| 57 | return y, nil // β βͺ y == y |
| 58 | case y == nil: |
| 59 | return x, nil // x βͺ β == x |
| 60 | case x.typ == nil: |
| 61 | return x, nil // π€ βͺ y == π€ |
| 62 | case y.typ == nil: |
| 63 | return y, nil // x βͺ π€ == π€ |
| 64 | } |
| 65 | // β β x, y β π€ |
| 66 | |
| 67 | if x.disjoint(y) { |
| 68 | return x, y // x βͺ y == (x, y) if x β© y == β |
| 69 | } |
| 70 | // x.typ == y.typ |
| 71 | |
| 72 | // ~t βͺ ~t == ~t |
| 73 | // ~t βͺ T == ~t |
| 74 | // T βͺ ~t == ~t |
| 75 | // T βͺ T == T |
| 76 | if x.tilde || !y.tilde { |
| 77 | return x, nil |
| 78 | } |
| 79 | return y, nil |
| 80 | } |
| 81 | |
| 82 | // intersect returns the intersection x β© y. |
| 83 | func (x *term) intersect(y *term) *term { |
| 84 | // easy cases |
| 85 | switch { |
| 86 | case x == nil || y == nil: |
| 87 | return nil // β β© y == β and β© β == β |
| 88 | case x.typ == nil: |
| 89 | return y // π€ β© y == y |
| 90 | case y.typ == nil: |
| 91 | return x // x β© π€ == x |
| 92 | } |
| 93 | // β β x, y β π€ |
| 94 | |
| 95 | if x.disjoint(y) { |
| 96 | return nil // x β© y == β if x β© y == β |
| 97 | } |
| 98 | // x.typ == y.typ |
| 99 | |
| 100 | // ~t β© ~t == ~t |
| 101 | // ~t β© T == T |
| 102 | // T β© ~t == T |
| 103 | // T β© T == T |
| 104 | if !x.tilde || y.tilde { |
| 105 | return x |
| 106 | } |
| 107 | return y |
| 108 | } |
| 109 | |
| 110 | // includes reports whether t β x. |
| 111 | func (x *term) includes(t types.Type) bool { |
| 112 | // easy cases |
| 113 | switch { |
| 114 | case x == nil: |
| 115 | return false // t β β == false |
| 116 | case x.typ == nil: |
| 117 | return true // t β π€ == true |
| 118 | } |
| 119 | // β β x β π€ |
| 120 | |
| 121 | u := t |
| 122 | if x.tilde { |
| 123 | u = under(u) |
| 124 | } |
| 125 | return types.Identical(x.typ, u) |
| 126 | } |
| 127 | |
| 128 | // subsetOf reports whether x β y. |
| 129 | func (x *term) subsetOf(y *term) bool { |
| 130 | // easy cases |
| 131 | switch { |
| 132 | case x == nil: |
| 133 | return true // β β y == true |
| 134 | case y == nil: |
| 135 | return false // x β β == false since x != β |
| 136 | case y.typ == nil: |
| 137 | return true // x β π€ == true |
| 138 | case x.typ == nil: |
| 139 | return false // π€ β y == false since y != π€ |
| 140 | } |
| 141 | // β β x, y β π€ |
| 142 | |
| 143 | if x.disjoint(y) { |
| 144 | return false // x β y == false if x β© y == β |
| 145 | } |
| 146 | // x.typ == y.typ |
| 147 | |
| 148 | // ~t β ~t == true |
| 149 | // ~t β T == false |
| 150 | // T β ~t == true |
| 151 | // T β T == true |
| 152 | return !x.tilde || y.tilde |
| 153 | } |
| 154 | |
| 155 | // disjoint reports whether x β© y == β . |
| 156 | // x.typ and y.typ must not be nil. |
| 157 | func (x *term) disjoint(y *term) bool { |
| 158 | if debug && (x.typ == nil || y.typ == nil) { |
| 159 | panic("invalid argument(s)") |
| 160 | } |
| 161 | ux := x.typ |
| 162 | if y.tilde { |
| 163 | ux = under(ux) |
| 164 | } |
| 165 | uy := y.typ |
| 166 | if x.tilde { |
| 167 | uy = under(uy) |
| 168 | } |
| 169 | return !types.Identical(ux, uy) |
| 170 | } |
| 171 |
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