diff options
Diffstat (limited to 'source/slang/slang-check-conformance.cpp')
| -rw-r--r-- | source/slang/slang-check-conformance.cpp | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/source/slang/slang-check-conformance.cpp b/source/slang/slang-check-conformance.cpp index 71b87f447..ba1b8ea55 100644 --- a/source/slang/slang-check-conformance.cpp +++ b/source/slang/slang-check-conformance.cpp @@ -122,6 +122,8 @@ SubtypeWitness* SemanticsVisitor::checkAndConstructSubtypeWitness( ensureDecl(superDeclRefType->getDeclRef().getDecl(), DeclCheckState::ReadyForLookup); } + SubtypeWitness* failureWitness = nullptr; + // In the common case, we can use the pre-computed inheritance information for `subType` // to enumerate all the types it transitively inherits from. // @@ -148,9 +150,19 @@ SubtypeWitness* SemanticsVisitor::checkAndConstructSubtypeWitness( // If the `superType` appears in the flattened inheritance list // for the `subType`, then we know that the subtype relationship - // holds. Conveniently, the `facet` stores a pre-computed witness - // for the subtype relationship, which we can return here. - // + // holds. + + // If the witness is optional, we should only return it if no certain + // witness was found. + auto declWitness = as<DeclaredSubtypeWitness>(facet->subtypeWitness); + if (declWitness && declWitness->isOptional()) + { + failureWitness = facet->subtypeWitness; + continue; + } + + // Conveniently, the `facet` stores a pre-computed witness for the + // subtype relationship, which we can use here. return facet->subtypeWitness; } // @@ -271,7 +283,7 @@ SubtypeWitness* SemanticsVisitor::checkAndConstructSubtypeWitness( return m_astBuilder->getEachSubtypeWitness(subType, superType, elementWitness); } // default is failure - return nullptr; + return failureWitness; } bool SemanticsVisitor::isValidGenericConstraintType(Type* type) |