[Compile Time Constant Extraction] Add @extractConstantsFromMembers (#69944)

Add @extractConstantsFromMembers attribute under ExtractConstantsFromMembers experimental feature flag

Author: ApolloZhu

include/swift/AST/Attr.def

@@ -533,6 +533,9 @@ CONTEXTUAL_SIMPLE_DECL_ATTR(_resultDependsOnSelf, ResultDependsOnSelf,
 SIMPLE_DECL_ATTR(_staticExclusiveOnly, StaticExclusiveOnly,
   OnStruct | UserInaccessible | ABIStableToAdd | ABIStableToRemove | APIBreakingToAdd | APIStableToRemove,
   151)
+SIMPLE_DECL_ATTR(extractConstantsFromMembers, ExtractConstantsFromMembers,
+  OnProtocol | UserInaccessible | ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,
+  152)
 
 #undef TYPE_ATTR
 #undef DECL_ATTR_ALIAS

include/swift/AST/DiagnosticsSema.def

@@ -1935,6 +1935,10 @@ ERROR(attr_static_exclusive_only_let_only_param,none,
 ERROR(attr_static_exclusive_only_mutating,none,
       "type %0 cannot have mutating function %1", (Type, ValueDecl *))
 
+// @extractConstantsFromMembers
+ERROR(attr_extractConstantsFromMembers_experimental,none,
+      "@extractConstantsFromMembers requires '-enable-experimental-feature ExtractConstantsFromMembers'", ())
+
 ERROR(c_func_variadic, none,
       "cannot declare variadic argument %0 in %kind1",
       (DeclName, const ValueDecl *))

include/swift/Basic/Features.def

@@ -263,6 +263,9 @@ EXPERIMENTAL_FEATURE(InferSendableFromCaptures, false)
 /// Enable the `@_staticExclusiveOnly` attribute.
 EXPERIMENTAL_FEATURE(StaticExclusiveOnly, true)
 
+/// Enable the @extractConstantsFromMembers attribute.
+EXPERIMENTAL_FEATURE(ExtractConstantsFromMembers, false)
+
 #undef EXPERIMENTAL_FEATURE_EXCLUDED_FROM_MODULE_INTERFACE
 #undef EXPERIMENTAL_FEATURE
 #undef UPCOMING_FEATURE

lib/AST/ASTPrinter.cpp

@@ -3648,6 +3648,10 @@ static bool usesFeatureStaticExclusiveOnly(Decl *decl) {
   return decl->getAttrs().hasAttribute<StaticExclusiveOnlyAttr>();
 }
 
+static bool usesFeatureExtractConstantsFromMembers(Decl *decl) {
+  return decl->getAttrs().hasAttribute<ExtractConstantsFromMembersAttr>();
+}
+
 /// Suppress the printing of a particular feature.
 static void suppressingFeature(PrintOptions &options, Feature feature,
                                llvm::function_ref<void()> action) {

lib/ConstExtract/ConstExtract.cpp

@@ -56,7 +56,8 @@ class NominalTypeConformanceCollector : public ASTWalker {
     if (auto *NTD = llvm::dyn_cast<NominalTypeDecl>(D))
       if (!isa<ProtocolDecl>(NTD))
         for (auto &Protocol : NTD->getAllProtocols())
-          if (Protocols.count(Protocol->getName().str().str()) != 0)
+          if (Protocol->getAttrs().hasAttribute<ExtractConstantsFromMembersAttr>() ||
+              Protocols.count(Protocol->getName().str().str()) != 0)
             ConformanceTypeDecls.push_back(NTD);
     return Action::Continue();
   }

lib/Sema/TypeCheckAttr.cpp

@@ -330,6 +330,8 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
 
   void visitAlwaysEmitConformanceMetadataAttr(AlwaysEmitConformanceMetadataAttr *attr);
 
+  void visitExtractConstantsFromMembersAttr(ExtractConstantsFromMembersAttr *attr);
+
   void visitUnavailableFromAsyncAttr(UnavailableFromAsyncAttr *attr);
 
   void visitUnsafeInheritExecutorAttr(UnsafeInheritExecutorAttr *attr);
@@ -430,6 +432,13 @@ void AttributeChecker::visitAlwaysEmitConformanceMetadataAttr(AlwaysEmitConforma
   return;
 }
 
+void AttributeChecker::visitExtractConstantsFromMembersAttr(ExtractConstantsFromMembersAttr *attr) {
+  if (!Ctx.LangOpts.hasFeature(Feature::ExtractConstantsFromMembers)) {
+    diagnoseAndRemoveAttr(attr,
+                          diag::attr_extractConstantsFromMembers_experimental);
+  }
+}
+
 void AttributeChecker::visitTransparentAttr(TransparentAttr *attr) {
   DeclContext *dc = D->getDeclContext();
   // Protocol declarations cannot be transparent.

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1622,6 +1622,7 @@ namespace  {
     UNINTERESTING_ATTR(UnsafeInheritExecutor)
     UNINTERESTING_ATTR(CompilerInitialized)
     UNINTERESTING_ATTR(AlwaysEmitConformanceMetadata)
+    UNINTERESTING_ATTR(ExtractConstantsFromMembers)
 
     UNINTERESTING_ATTR(EagerMove)
     UNINTERESTING_ATTR(NoEagerMove)

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 820; // begin_borrow/move_value [var_decl]
+const uint16_t SWIFTMODULE_VERSION_MINOR = 821; // extractConstantsFromMembers
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///

test/ConstExtraction/ExtractConstantsFromMembersAttribute.swift

@@ -0,0 +1,18 @@
+// RUN: %empty-directory(%t)
+// RUN: echo "[]" > %t/protocols.json
+
+// RUN: %target-swift-frontend -typecheck -emit-const-values-path %t/ExtractConstantsFromMembersAttribute.swiftconstvalues -const-gather-protocols-file %t/protocols.json -primary-file %s -enable-experimental-feature ExtractConstantsFromMembers
+// RUN: cat %t/ExtractConstantsFromMembersAttribute.swiftconstvalues 2>&1 | %FileCheck %s
+
+@extractConstantsFromMembers protocol MyProto {}
+public struct TestStruct : MyProto {
+    let foo = "foo"
+    let cane: [String] = ["bar", "baz"]
+}
+
+// CHECK:             "label": "foo",
+// CHECK:             "valueKind": "RawLiteral",
+// CHECK:             "value": "foo"
+
+// CHECK:             "label": "cane",
+// CHECK-NEXT:        "type": "Swift.Array<Swift.String>",

test/ConstExtraction/ExtractConstantsFromMembersAttributeExperimental.swift

@@ -0,0 +1,4 @@
+// RUN: %target-typecheck-verify-swift %s
+
+// expected-error@+1{{@extractConstantsFromMembers requires '-enable-experimental-feature ExtractConstantsFromMembers'}}
+@extractConstantsFromMembers protocol MyProto {}