ABI checker: diagnose the missing of @available attributes for added ABIs

New ABIs should have an @available attribute to describe the introducing
version. This patch teaches the tool to diagnose its missing.

Decls with @_AlwaysEmitIntoClient are excluded from the blaming lists since
they are essentially available all the time.

rdar://51089418

include/swift/AST/DiagnosticsModuleDiffer.def

@@ -96,6 +96,8 @@ ERROR(type_witness_change,none,"%0 has type witness type for %1 changing from %2
 
 ERROR(decl_new_witness_table_entry,none,"%0 now requires %select{|no}1 new witness table entry", (StringRef, bool))
 
+ERROR(new_decl_without_intro,none,"%0 is a new API without @available attribute", (StringRef))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

test/api-digester/Outputs/Cake-abi.txt

@@ -57,6 +57,20 @@ cake1: Var C1.CIIns1 changes from weak to strong
 cake1: Var C1.CIIns2 changes from strong to weak
 cake1: Var GlobalLetChangedToVar changes from let to var
 cake1: Var GlobalVarChangedToLet changes from var to let
+cake2: Accessor GlobalLetChangedToVar.Set() is a new API without @available attribute
+cake2: Accessor fixedLayoutStruct2.BecomeFixedBinaryOrder.Set() is a new API without @available attribute
+cake2: AssociatedType RequiementChanges.addedTypeWithDefault is a new API without @available attribute
+cake2: AssociatedType RequiementChanges.addedTypeWithoutDefault is a new API without @available attribute
+cake2: Class C0 is a new API without @available attribute
+cake2: Class C8 is a new API without @available attribute
+cake2: Constructor C1.init(_:) is a new API without @available attribute
+cake2: EnumElement FrozenKind.AddedCase is a new API without @available attribute
+cake2: Func RequiementChanges.addedFunc() is a new API without @available attribute
+cake2: Func fixedLayoutStruct.OKChange() is a new API without @available attribute
+cake2: Protocol P4 is a new API without @available attribute
+cake2: Var RequiementChanges.addedVar is a new API without @available attribute
+cake2: Var fixedLayoutStruct.$__lazy_storage_$_lazy_d is a new API without @available attribute
+cake2: Var fixedLayoutStruct.c is a new API without @available attribute
 
 /* Fixed-layout Type changes */
 cake1: EnumElement FrozenKind.Fixed in a non-resilient type changes position from 1 to 2

test/api-digester/Outputs/cake-abi.json

@@ -1035,6 +1035,10 @@
           "moduleName": "cake",
           "genericSig": "<τ_0_0 where τ_0_0 : PSuper>",
           "isABIPlaceholder": true,
+          "intro_Macosx": "9999",
+          "intro_iOS": "9999",
+          "intro_tvOS": "9999",
+          "intro_watchOS": "9999",
           "funcSelfKind": "NonMutating"
         }
       ],

test/api-digester/Outputs/cake.json

@@ -982,6 +982,10 @@
           "moduleName": "cake",
           "genericSig": "<Self where Self : PSuper>",
           "isABIPlaceholder": true,
+          "intro_Macosx": "9999",
+          "intro_iOS": "9999",
+          "intro_tvOS": "9999",
+          "intro_watchOS": "9999",
           "funcSelfKind": "NonMutating"
         }
       ],

test/api-digester/Outputs/stability-stdlib-abi.swift.expected

@@ -1,3 +1,14 @@
+// The init(signOf:magnitudeOf:) blames are false positives. They are not new APIs.
+Constructor Double.init(signOf:magnitudeOf:) is a new API without @available attribute
+Constructor Float.init(signOf:magnitudeOf:) is a new API without @available attribute
+Constructor Float80.init(signOf:magnitudeOf:) is a new API without @available attribute
+
+Constructor __RawDictionaryStorage.init(coder:) is a new API without @available attribute
+Constructor __RawSetStorage.init(coder:) is a new API without @available attribute
+Constructor __SwiftNativeNSData.init(coder:) is a new API without @available attribute
+Constructor __SwiftNativeNSDictionary.init(coder:) is a new API without @available attribute
+Constructor __SwiftNativeNSSet.init(coder:) is a new API without @available attribute
+
 Func _cos(_:) has been removed
 Func _exp(_:) has been removed
 Func _exp2(_:) has been removed

tools/swift-api-digester/ModuleAnalyzerNodes.cpp

@@ -1145,6 +1145,8 @@ static bool isABIPlaceholderRecursive(Decl *D) {
 }
 
 StringRef SDKContext::getPlatformIntroVersion(Decl *D, PlatformKind Kind) {
+  if (!D)
+    return StringRef();
   for (auto *ATT: D->getAttrs()) {
     if (auto *AVA = dyn_cast<AvailableAttr>(ATT)) {
       if (AVA->Platform == Kind && AVA->Introduced) {
@@ -1152,10 +1154,12 @@ StringRef SDKContext::getPlatformIntroVersion(Decl *D, PlatformKind Kind) {
       }
     }
   }
-  return StringRef();
+  return getPlatformIntroVersion(D->getDeclContext()->getAsDecl(), Kind);
 }
 
 StringRef SDKContext::getLanguageIntroVersion(Decl *D) {
+  if (!D)
+    return StringRef();
   for (auto *ATT: D->getAttrs()) {
     if (auto *AVA = dyn_cast<AvailableAttr>(ATT)) {
       if (AVA->isLanguageVersionSpecific() && AVA->Introduced) {
@@ -1163,7 +1167,7 @@ StringRef SDKContext::getLanguageIntroVersion(Decl *D) {
       }
     }
   }
-  return StringRef();
+  return getLanguageIntroVersion(D->getDeclContext()->getAsDecl());
 }
 
 SDKNodeInitInfo::SDKNodeInitInfo(SDKContext &Ctx, Type Ty, TypeInitInfo Info) :

tools/swift-api-digester/ModuleAnalyzerNodes.h

@@ -293,6 +293,9 @@ struct PlatformIntroVersion {
   StringRef tvos;
   StringRef watchos;
   StringRef swift;
+  bool hasOSAvailability() const {
+    return !macos.empty() || !ios.empty() || !tvos.empty() || !watchos.empty();
+  }
 };
 
 class SDKNodeDecl: public SDKNode {
@@ -347,6 +350,7 @@ public:
   StringRef getScreenInfo() const;
   bool hasFixedBinaryOrder() const { return FixedBinaryOrder.hasValue(); }
   uint8_t getFixedBinaryOrder() const { return *FixedBinaryOrder; }
+  PlatformIntroVersion getIntroducingVersion() const { return introVersions; }
   virtual void jsonize(json::Output &Out) override;
   virtual void diagnose(SDKNode *Right) override;
 

tools/swift-api-digester/ModuleDiagsConsumer.cpp

@@ -44,6 +44,7 @@ static StringRef getCategoryName(uint32_t ID) {
   case LocalDiagID::decl_new_attr:
   case LocalDiagID::var_let_changed:
   case LocalDiagID::func_self_access_change:
+  case LocalDiagID::new_decl_without_intro:
     return "/* Decl Attribute changes */";
   case LocalDiagID::default_arg_removed:
   case LocalDiagID::decl_type_change:

tools/swift-api-digester/swift-api-digester.cpp

@@ -1003,6 +1003,13 @@ public:
           if (D->hasFixedBinaryOrder()) {
             D->emitDiag(diag::decl_added);
           }
+          // Diagnose the missing of @available attributes.
+          // Decls with @_alwaysEmitIntoClient aren't required to have an
+          // @available attribute.
+          if (!D->getIntroducingVersion().hasOSAvailability() &&
+              !D->hasDeclAttribute(DeclAttrKind::DAK_AlwaysEmitIntoClient)) {
+            D->emitDiag(diag::new_decl_without_intro);
+          }
         }
       }
       // Complain about added protocol requirements
@@ -1038,7 +1045,6 @@ public:
           }
         }
       }
-
       return;
     case NodeMatchReason::Removed:
       assert(!Right);