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Parameterize conformance lookup on whether "missing" conformances are allowed.

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Many clients of the conformance lookup operations would prefer to get
an invalid conformance (== there is no conformance) rather than a
missing conformance. Parameterize the conformance lookup operations so
that most callers won't see missing conformances, by filtering them
out at the end. Opt-in those callers that do want to see missing
conformances so they can be diagnosed.
This commit is contained in:
Doug Gregor
2021-07-30 07:54:23 -07:00
parent de44396bd2
commit f9c34756ef
13 changed files with 75 additions and 45 deletions
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23
lib/AST/Module.cpp
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@@ -970,8 +970,14 @@ ModuleDecl::lookupExistentialConformance(Type type, ProtocolDecl *protocol) {
return ProtocolConformanceRef::forInvalid();
}
/// Whether we should create missing conformances to the given protocol.
static bool shouldCreateMissingConformances(ProtocolDecl *proto) {
return proto->isSpecificProtocol(KnownProtocolKind::Sendable);
}
ProtocolConformanceRef ModuleDecl::lookupConformance(Type type,
ProtocolDecl *protocol) {
ProtocolDecl *protocol,
bool allowMissing) {
// If we are recursively checking for implicit conformance of a nominal
// type to Sendable, fail without evaluating this request. This
// squashes cycles.
@@ -985,18 +991,27 @@ ProtocolConformanceRef ModuleDecl::lookupConformance(Type type,
}
}
return evaluateOrDefault(
auto result = evaluateOrDefault(
getASTContext().evaluator, request, ProtocolConformanceRef::forInvalid());
// If we aren't supposed to allow missing conformances through for this
// protocol, replace the result with an "invalid" result.
if (!allowMissing &&
shouldCreateMissingConformances(protocol) &&
result.hasMissingConformance(this))
return ProtocolConformanceRef::forInvalid();
return result;
}
/// Retrieve an invalid or missing conformance, as appropriate, when a
/// legitimate conformance doesn't exist.
static ProtocolConformanceRef getInvalidOrMissingConformance(
Type type, ProtocolDecl *proto) {
// Introduce "missing" conformances to Sendable, so that type checking
// Introduce "missing" conformances when appropriate, so that type checking
// (and even code generation) can continue.
ASTContext &ctx = proto->getASTContext();
if (proto->isSpecificProtocol(KnownProtocolKind::Sendable)) {
if (shouldCreateMissingConformances(proto)) {
return ProtocolConformanceRef(
ctx.getBuiltinConformance(
type, proto, GenericSignature(), { },