Key cache by SourceFile.

Author: David Ungar

include/swift/AST/ASTContext.h

@@ -942,7 +942,8 @@ class ASTContext final {
     return !LangOpts.EnableAccessControl;
   }
 
-  llvm::SmallVectorImpl<Type> &getDefaultTypeRequestCache();
+  /// Logically, there is a separate cache for each SourceFile.
+  llvm::SmallVectorImpl<Type> &getDefaultTypeRequestCache(SourceFile*);
 
 private:
   friend Decl;

lib/AST/ASTContext.cpp

@@ -290,11 +290,10 @@ FOR_KNOWN_FOUNDATION_TYPES(CACHE_FOUNDATION_DECL)
                  ProtocolConformanceRef>
     DefaultAssociatedConformanceWitnesses;
 
-  /// Cache of default types for DefaultTypeRequest.
+  /// Caches of default types for DefaultTypeRequest.
   /// Used to be instance variables in the TypeChecker.
-  /// Soon to become more specific.
-  llvm::SmallVector<Type, NumKnownProtocols> DefaultTypeRequestCache{
-      NumKnownProtocols, Type()};
+  /// There is a logically separate cache for each SourceFile.
+  llvm::DenseMap<SourceFile*, llvm::SmallVector<Type, NumKnownProtocols>> DefaultTypeRequestCaches;
 
   /// Structure that captures data that is segregated into different
   /// arenas.
@@ -5080,6 +5079,6 @@ LayoutConstraint LayoutConstraint::getLayoutConstraint(LayoutConstraintKind Kind
   return LayoutConstraint(New);
 }
 
-llvm::SmallVectorImpl<Type> &ASTContext::getDefaultTypeRequestCache() {
-  return getImpl().DefaultTypeRequestCache;
+llvm::SmallVectorImpl<Type> &ASTContext::getDefaultTypeRequestCache(SourceFile* SF) {
+  return getImpl().DefaultTypeRequestCaches[SF];
 }

lib/AST/TypeCheckRequests.cpp

@@ -457,7 +457,7 @@ SourceFile *DefaultTypeRequest::getSourceFile() const {
 }
 
 llvm::SmallVectorImpl<Type> &DefaultTypeRequest::getCache() const {
-  return getDeclContext()->getASTContext().getDefaultTypeRequestCache();
+  return getDeclContext()->getASTContext().getDefaultTypeRequestCache(getSourceFile());
 }
 
 Optional<Type> DefaultTypeRequest::getCachedResult() const {