-
Notifications
You must be signed in to change notification settings - Fork 10.5k
/
Copy pathconditional_conformance_with_assoc.swift
254 lines (210 loc) · 15.4 KB
/
conditional_conformance_with_assoc.swift
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
public func takes_p1<T: P1>(_: T.Type) {}
public protocol P1 {
associatedtype AT1
func normal()
func generic<T: P3>(_: T)
}
public protocol P2 {
associatedtype AT2: P3
}
public protocol P3 {
associatedtype AT3
}
public struct Nothing {}
public struct IsP2: P2 {
public typealias AT2 = IsP3
}
public struct IsP3: P3 {
public typealias AT3 = Nothing
}
public struct IsAlsoP2: P2 {
public typealias AT2 = IsBoth
}
public struct IsBoth: P2, P3 {
public typealias AT2 = HoldsP3
public typealias AT3 = Nothing
}
public struct HoldsP3: P3 {
public typealias AT3 = IsP3
}
public struct Double<B: P2, C> {}
extension Double: P1 where B.AT2: P2, C: P3, B.AT2.AT2.AT3: P3 {
public typealias AT1 = C
public func normal() {}
public func generic<T: P3>(_: T) {}
}
// witness method for Double.normal
// CHECK-LABEL: define linkonce_odr hidden swiftcc void @"$s34conditional_conformance_with_assoc6DoubleVyxq_GAA2P1A2A2P3R_AA2P23AT2RpzAafH_AhaGP3AT3RPzrlAaEP6normalyyFTW"(%T34conditional_conformance_with_assoc6DoubleV* noalias nocapture swiftself %0, %swift.type* %Self, i8** %SelfWitnessTable)
// CHECK-NEXT: entry:
// CHECK-NEXT: [[C_P3_PTR:%.*]] = getelementptr inbounds i8*, i8** %SelfWitnessTable, i32 -1
// CHECK-NEXT: [[C_P3:%.*]] = load i8*, i8** [[C_P3_PTR]], align 8
// CHECK-NEXT: %"\CF\84_0_1.P3" = bitcast i8* [[C_P3]] to i8**
// CHECK-NEXT: [[B_AT2_P2_PTR:%.*]] = getelementptr inbounds i8*, i8** %SelfWitnessTable, i32 -2
// CHECK-NEXT: [[B_AT2_P2:%.*]] = load i8*, i8** [[B_AT2_P2_PTR]], align 8
// CHECK-NEXT: %"\CF\84_0_0.AT2.P2" = bitcast i8* [[B_AT2_P2]] to i8**
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3_PTR:%.*]] = getelementptr inbounds i8*, i8** %SelfWitnessTable, i32 -3
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3:%.*]] = load i8*, i8** [[B_AT2_AT2_AT3_P3_PTR]], align 8
// CHECK-NEXT: %"\CF\84_0_0.AT2.AT2.AT3.P3" = bitcast i8* [[B_AT2_AT2_AT3_P3]] to i8**
// CHECK-NEXT: [[SELF_AS_TYPE_ARRAY:%.*]] = bitcast %swift.type* %Self to %swift.type**
// CHECK-NEXT: [[B_PTR:%.*]] = getelementptr inbounds %swift.type*, %swift.type** [[SELF_AS_TYPE_ARRAY]], i64 2
// CHECK-NEXT: [[B:%.*]] = load %swift.type*, %swift.type** [[B_PTR]], align 8
// CHECK-NEXT: [[SELF_AS_TYPE_ARRAY_2:%.*]] = bitcast %swift.type* %Self to %swift.type**
// CHECK-NEXT: [[C_PTR:%.*]] = getelementptr inbounds %swift.type*, %swift.type** [[SELF_AS_TYPE_ARRAY_2]], i64 3
// CHECK-NEXT: [[C:%.*]] = load %swift.type*, %swift.type** [[C_PTR]], align 8
// CHECK-NEXT: [[SELF_AS_WT_ARRAY:%.*]] = bitcast %swift.type* %Self to i8***
// CHECK-NEXT: [[B_P2_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[SELF_AS_WT_ARRAY]], i64 4
// CHECK-NEXT: %"\CF\84_0_0.P2" = load i8**, i8*** [[B_P2_PTR]], align 8
// CHECK-NEXT: call swiftcc void @"$s34conditional_conformance_with_assoc6DoubleVA2A2P3R_AA2P23AT2RpzAadF_AfaEP3AT3RPzrlE6normalyyF"(%swift.type* %"\CF\84_0_0", %swift.type* %"\CF\84_0_1", i8** %"\CF\84_0_0.P2", i8** %"\CF\84_0_1.P3", i8** %"\CF\84_0_0.AT2.P2", i8** %"\CF\84_0_0.AT2.AT2.AT3.P3")
// CHECK-NEXT: ret void
// CHECK-NEXT: }
// witness method for Double.generic
// CHECK-LABEL: define linkonce_odr hidden swiftcc void @"$s34conditional_conformance_with_assoc6DoubleVyxq_GAA2P1A2A2P3R_AA2P23AT2RpzAafH_AhaGP3AT3RPzrlAaEP7genericyyqd__AaFRd__lFTW"(%swift.opaque* noalias nocapture %0, %swift.type* %"\CF\84_1_0", i8** %"\CF\84_1_0.P3", %T34conditional_conformance_with_assoc6DoubleV* noalias nocapture swiftself %1, %swift.type* %Self, i8** %SelfWitnessTable)
// CHECK-NEXT: entry:
// CHECK-NEXT: [[C_P3_PTR:%.*]] = getelementptr inbounds i8*, i8** %SelfWitnessTable, i32 -1
// CHECK-NEXT: [[C_P3:%.*]] = load i8*, i8** [[C_P3_PTR]], align 8
// CHECK-NEXT: %"\CF\84_0_1.P3" = bitcast i8* [[C_P3]] to i8**
// CHECK-NEXT: [[B_AT2_P2_PTR:%.*]] = getelementptr inbounds i8*, i8** %SelfWitnessTable, i32 -2
// CHECK-NEXT: [[B_AT2_P2:%.*]] = load i8*, i8** [[B_AT2_P2_PTR]], align 8
// CHECK-NEXT: %"\CF\84_0_0.AT2.P2" = bitcast i8* [[B_AT2_P2]] to i8**
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3_PTR:%.*]] = getelementptr inbounds i8*, i8** %SelfWitnessTable, i32 -3
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3:%.*]] = load i8*, i8** [[B_AT2_AT2_AT3_P3_PTR]], align 8
// CHECK-NEXT: %"\CF\84_0_0.AT2.AT2.AT3.P3" = bitcast i8* [[B_AT2_AT2_AT3_P3]] to i8**
// CHECK-NEXT: [[SELF_AS_TYPE_ARRAY:%.*]] = bitcast %swift.type* %Self to %swift.type**
// CHECK-NEXT: [[B_PTR:%.*]] = getelementptr inbounds %swift.type*, %swift.type** [[SELF_AS_TYPE_ARRAY]], i64 2
// CHECK-NEXT: [[B:%.*]] = load %swift.type*, %swift.type** [[B_PTR]], align 8
// CHECK-NEXT: [[SELF_AS_TYPE_ARRAY_2:%.*]] = bitcast %swift.type* %Self to %swift.type**
// CHECK-NEXT: [[C_PTR:%.*]] = getelementptr inbounds %swift.type*, %swift.type** [[SELF_AS_TYPE_ARRAY_2]], i64 3
// CHECK-NEXT: [[C:%.*]] = load %swift.type*, %swift.type** [[C_PTR]], align 8
// CHECK-NEXT: [[SELF_AS_WT_ARRAY:%.*]] = bitcast %swift.type* %Self to i8***
// CHECK-NEXT: [[B_P2_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[SELF_AS_WT_ARRAY]], i64 4
// CHECK-NEXT: %"\CF\84_0_0.P2" = load i8**, i8*** [[B_P2_PTR]], align 8
// CHECK-NEXT: call swiftcc void @"$s34conditional_conformance_with_assoc6DoubleVA2A2P3R_AA2P23AT2RpzAadF_AfaEP3AT3RPzrlE7genericyyqd__AaDRd__lF"(%swift.opaque* noalias nocapture %0, %swift.type* %"\CF\84_0_0", %swift.type* %"\CF\84_0_1", %swift.type* %"\CF\84_1_0", i8** %"\CF\84_0_0.P2", i8** %"\CF\84_0_1.P3", i8** %"\CF\84_1_0.P3", i8** %"\CF\84_0_0.AT2.P2", i8** %"\CF\84_0_0.AT2.AT2.AT3.P3")
// CHECK-NEXT: ret void
// CHECK-NEXT: }
public func generic_generic<T: P2, U>(_: T.Type, _: U.Type)
where T.AT2: P2, U: P3, T.AT2.AT2.AT3: P3
{
takes_p1(Double<T, U>.self)
}
// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc void @"$s34conditional_conformance_with_assoc08generic_E0yyxm_q_mtAA2P2RzAA2P3R_AaC3AT2RpzAadE_AeaCP3AT3RPzr0_lF"(%swift.type* %0, %swift.type* %1, %swift.type* %T, %swift.type* %U, i8** %T.P2, i8** %U.P3, i8** %T.AT2.P2, i8** %T.AT2.AT2.AT3.P3)
// CHECK-NEXT: entry:
// CHECK: %conditional.requirement.buffer = alloca [3 x i8**], align 8
// CHECK: [[T0:%.*]] = call swiftcc %swift.metadata_response @"$s34conditional_conformance_with_assoc6DoubleVMa"(i64 0, %swift.type* %T, %swift.type* %U, i8** %T.P2)
// CHECK-NEXT: [[Double_TYPE:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
// CHECK-NEXT: [[CONDITIONAL_REQUIREMENTS:%.*]] = getelementptr inbounds [3 x i8**], [3 x i8**]* %conditional.requirement.buffer, i32 0, i32 0
// CHECK-NEXT: [[C_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 0
// CHECK-NEXT: store i8** %U.P3, i8*** [[C_P3_PTR]], align 8
// CHECK-NEXT: [[B_AT2_P2_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 1
// CHECK-NEXT: store i8** %T.AT2.P2, i8*** [[B_AT2_P2_PTR]], align 8
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 2
// CHECK-NEXT: store i8** %T.AT2.AT2.AT3.P3, i8*** [[B_AT2_AT2_AT3_P3_PTR]], align 8
// CHECK-NEXT: [[Double_P1:%.*]] = call i8** @swift_getWitnessTable
// CHECK-NEXT: call swiftcc void @"$s34conditional_conformance_with_assoc8takes_p1yyxmAA2P1RzlF"(%swift.type* [[Double_TYPE]], %swift.type* [[Double_TYPE]], i8** [[Double_P1]])
// CHECK-NEXT: ret void
// CHECK-NEXT: }
public func generic_concrete<T: P2>(_: T.Type)
where T.AT2: P2, T.AT2.AT2.AT3: P3
{
takes_p1(Double<T, IsP3>.self)
}
// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc void @"$s34conditional_conformance_with_assoc16generic_concreteyyxmAA2P2RzAaC3AT2RpzAA2P3AD_AdaCP3AT3RPzlF"(%swift.type* %0, %swift.type* %T, i8** %T.P2, i8** %T.AT2.P2, i8** %T.AT2.AT2.AT3.P3)
// CHECK-NEXT: entry:
// CHECK: %conditional.requirement.buffer = alloca [3 x i8**], align 8
// CHECK: [[T0:%.*]] = call swiftcc %swift.metadata_response @"$s34conditional_conformance_with_assoc6DoubleVMa"(
// CHECK-SAME: i64 0,
// CHECK-SAME: %swift.type*
// CHECK-SAME: %T,
// CHECK-SAME: %swift.type* bitcast (
// CHECK-SAME: i64* getelementptr inbounds (
// CHECK-SAME: <{
// CHECK-SAME: i8**,
// CHECK-SAME: i64,
// CHECK-SAME: <{ {{[^}]*}} }>*
// CHECK-SAME: }>,
// CHECK-SAME: <{ {{.*}} }>* @"$s34conditional_conformance_with_assoc4IsP3VMf",
// CHECK-SAME: i32 0,
// CHECK-SAME: i32 1
// CHECK-SAME: ) to %swift.type*
// CHECK-SAME: ),
// CHECK-SAME: i8** %T.P2
// CHECK-SAME: )
// CHECK-NEXT: [[Double_TYPE:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
// CHECK-NEXT: [[CONDITIONAL_REQUIREMENTS:%.*]] = getelementptr inbounds [3 x i8**], [3 x i8**]* %conditional.requirement.buffer, i32 0, i32 0
// CHECK-NEXT: [[C_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 0
// CHECK-NEXT: store i8** getelementptr inbounds ([2 x i8*], [2 x i8*]* @"$s34conditional_conformance_with_assoc4IsP3VAA0F0AAWP", i32 0, i32 0), i8*** [[C_P3_PTR]], align 8
// CHECK-NEXT: [[B_AT2_P2_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 1
// CHECK-NEXT: store i8** %T.AT2.P2, i8*** [[B_AT2_P2_PTR]], align 8
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 2
// CHECK-NEXT: store i8** %T.AT2.AT2.AT3.P3, i8*** [[B_AT2_AT2_AT3_P3_PTR]], align 8
// CHECK-NEXT: [[Double_P1:%.*]] = call i8** @swift_getWitnessTable
// CHECK-NEXT: call swiftcc void @"$s34conditional_conformance_with_assoc8takes_p1yyxmAA2P1RzlF"(%swift.type* [[Double_TYPE]], %swift.type* [[Double_TYPE]], i8** [[Double_P1]])
// CHECK-NEXT: ret void
// CHECK-NEXT: }
public func concrete_generic<U>(_: U.Type)
where U: P3
{
takes_p1(Double<IsAlsoP2, U>.self)
}
// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc void @"$s34conditional_conformance_with_assoc16concrete_genericyyxmAA2P3RzlF"(%swift.type* %0, %swift.type* %U, i8** %U.P3)
// CHECK-NEXT: entry:
// CHECK: %conditional.requirement.buffer = alloca [3 x i8**], align 8
// CHECK: [[T0:%.*]] = call swiftcc %swift.metadata_response @"$s34conditional_conformance_with_assoc6DoubleVMa"(i64 0, %swift.type* bitcast (i64* getelementptr inbounds (<{ {{.*}} }>, <{ {{.*}} }>* @"$s34conditional_conformance_with_assoc8IsAlsoP2VMf", i32 0, i32 1) to %swift.type*), %swift.type* %U, i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @"$s34conditional_conformance_with_assoc8IsAlsoP2VAA0G0AAWP", i32 0, i32 0))
// CHECK-NEXT: [[Double_TYPE:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
// CHECK-NEXT: [[CONDITIONAL_REQUIREMENTS:%.*]] = getelementptr inbounds [3 x i8**], [3 x i8**]* %conditional.requirement.buffer, i32 0, i32 0
// CHECK-NEXT: [[C_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 0
// CHECK-NEXT: store i8** %U.P3, i8*** [[C_P3_PTR]], align 8
// CHECK-NEXT: [[B_AT2_P2_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 1
// CHECK-NEXT: store i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @"$s34conditional_conformance_with_assoc6IsBothVAA2P2AAWP", i32 0, i32 0), i8*** [[B_AT2_P2_PTR]], align 8
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 2
// CHECK-NEXT: store i8** getelementptr inbounds ([2 x i8*], [2 x i8*]* @"$s34conditional_conformance_with_assoc4IsP3VAA0F0AAWP", i32 0, i32 0), i8*** [[B_AT2_AT2_AT3_P3_PTR]], align 8
// CHECK-NEXT: [[Double_P1:%.*]] = call i8** @swift_getWitnessTable
// CHECK-NEXT: call swiftcc void @"$s34conditional_conformance_with_assoc8takes_p1yyxmAA2P1RzlF"(%swift.type* [[Double_TYPE]], %swift.type* [[Double_TYPE]], i8** [[Double_P1]])
// CHECK-NEXT: ret void
// CHECK-NEXT:}
public func concrete_concrete() {
takes_p1(Double<IsAlsoP2, IsP3>.self)
}
// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc void @"$s34conditional_conformance_with_assoc09concrete_E0yyF"()
// CHECK-NEXT: entry:
// CHECK-NEXT: [[X:%.*]] = call {{.*}} @__swift_instantiateConcreteTypeFromMangledName({{.*}} @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGMD")
// CHECK-NEXT: [[Z:%.*]] = call i8** @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGACyxq_GAA2P1A2A0I0R_AA0H03AT2RpzAakM_AmaLP3AT3RPzrlWl"()
// CHECK-NEXT: call swiftcc void @"$s34conditional_conformance_with_assoc8takes_p1yyxmAA2P1RzlF"(%swift.type* [[X]], %swift.type* [[X]], i8** [[Z]])
// CHECK-NEXT: ret void
// CHECK-NEXT: }
// Lazy witness table accessor for the concrete Double<IsAlsoP2, IsP3> : P1.
// CHECK-LABEL: define linkonce_odr hidden i8** @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGACyxq_GAA2P1A2A0I0R_AA0H03AT2RpzAakM_AmaLP3AT3RPzrlWl"()
// CHECK-NEXT: entry:
// CHECK-NEXT: %conditional.requirement.buffer = alloca [3 x i8**], align 8
// CHECK-NEXT: [[CACHE:%.*]] = load i8**, i8*** @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGACyxq_GAA2P1A2A0I0R_AA0H03AT2RpzAakM_AmaLP3AT3RPzrlWL", align 8
// CHECK-NEXT: [[IS_NULL:%.*]] = icmp eq i8** [[CACHE]], null
// CHECK-NEXT: br i1 [[IS_NULL]], label %cacheIsNull, label %cont
// CHECK: cacheIsNull:
// CHECK-STABLE-ABI-FALSE-NEXT: [[T0:%.*]] = call swiftcc %swift.metadata_response @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGMa"(i64 255)
// CHECK-STABLE-ABI-FALSE-NEXT: [[Double_TYPE:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
// CHECK-STABLE-ABI-FALSE-NEXT: extractvalue %swift.metadata_response [[T0]], 1
// CHECK-STABLE-ABI-TRUE-NEXT: [[T0:%.*]] = call %swift.type* @__swift_instantiateConcreteTypeFromMangledNameAbstract({ i32, i32 }* @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGMD")
// CHECK-NEXT: [[CONDITIONAL_REQUIREMENTS:%.*]] = getelementptr inbounds [3 x i8**], [3 x i8**]* %conditional.requirement.buffer, i32 0, i32 0
// CHECK-NEXT: [[C_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 0
// CHECK-NEXT: store i8** getelementptr inbounds ([2 x i8*], [2 x i8*]* @"$s34conditional_conformance_with_assoc4IsP3VAA0F0AAWP", i32 0, i32 0), i8*** [[C_P3_PTR]], align 8
// CHECK-NEXT: [[B_AT2_P2_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 1
// CHECK-NEXT: store i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @"$s34conditional_conformance_with_assoc6IsBothVAA2P2AAWP", i32 0, i32 0), i8*** [[B_AT2_P2_PTR]], align 8
// CHECK-NEXT: [[B_AT2_AT2_AT3_P3_PTR:%.*]] = getelementptr inbounds i8**, i8*** [[CONDITIONAL_REQUIREMENTS]], i32 2
// CHECK-NEXT: store i8** getelementptr inbounds ([2 x i8*], [2 x i8*]* @"$s34conditional_conformance_with_assoc4IsP3VAA0F0AAWP", i32 0, i32 0), i8*** [[B_AT2_AT2_AT3_P3_PTR]], align 8
// CHECK-NEXT: [[Double_P1:%.*]] = call i8** @swift_getWitnessTable
// CHECK-NEXT: store atomic i8** [[Double_P1]], i8*** @"$s34conditional_conformance_with_assoc6DoubleVyAA8IsAlsoP2VAA0F2P3VGACyxq_GAA2P1A2A0I0R_AA0H03AT2RpzAakM_AmaLP3AT3RPzrlWL" release, align 8
// CHECK-NEXT: br label %cont
// CHECK: cont:
// CHECK-NEXT: [[T0:%.*]] = phi i8** [ [[CACHE]], %entry ], [ [[Double_P1]], %cacheIsNull ]
// CHECK-NEXT: ret i8** [[T0]]
// CHECK-NEXT: }
protocol Base {
}
protocol Sub : Base {
associatedtype S : Base
}
struct X<T> {
}
extension X: Base where T: Base { }
extension X: Sub where T: Sub, T.S == T {
typealias S = X<T>
}