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RequirementMachine: Reduction order on symbols should compare associated type name before protocols #39241

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Merged
merged 1 commit into from
Sep 10, 2021
Merged

RequirementMachine: Reduction order on symbols should compare associated type name before protocols #39241

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4 changes: 3 additions & 1 deletion lib/AST/RequirementMachine/Symbol.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -506,6 +506,9 @@ int Symbol::compare(Symbol other, const ProtocolGraph &graph) const {
auto protos = getProtocols();
auto otherProtos = other.getProtocols();

if (getName() != other.getName())
return getName().compare(other.getName());

// Symbols with more protocols are 'smaller' than those with fewer.
if (protos.size() != otherProtos.size())
return protos.size() > otherProtos.size() ? -1 : 1;
Expand All @@ -516,7 +519,6 @@ int Symbol::compare(Symbol other, const ProtocolGraph &graph) const {
return result;
}

result = getName().compare(other.getName());
break;
}

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17 changes: 17 additions & 0 deletions test/Generics/associated_type_order.swift
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@@ -0,0 +1,17 @@
// RUN: %target-swift-emit-silgen %s -requirement-machine=on | %FileCheck %s

protocol P1 {
associatedtype B
}

protocol P2 {
associatedtype A
}

// Make sure that T.[P1:A] < T.[P2:B].

struct G<T : P1 & P2> where T.A == T.B {
// CHECK-LABEL: sil hidden [ossa] @$s21associated_type_order1GV3fooyy1AAA2P2PQzF : $@convention(method) <T where T : P1, T : P2, T.A == T.B> (@in_guaranteed T.A, G<T>) -> () {
func foo(_: T.A) {}
}