Use enum as type tags instead of integer constants.

This is done to enable exhaustiveness in switch statements using the
tags, as they are required to cover all enum values, unlike ints.

Additionally, enum values better demonstrate intent.

Change-Id: I8d6de7a12fce059069cf74fe11c381cb70beb8a7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/437580
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: fshcheglov

pkg/analyzer/lib/src/dart/analysis/driver.dart

@@ -110,7 +110,7 @@ testFineAfterLibraryAnalyzerHook;
 // TODO(scheglov): Clean up the list of implicitly analyzed files.
 class AnalysisDriver {
   /// The version of data format, should be incremented on every format change.
-  static const int DATA_VERSION = 482;
+  static const int DATA_VERSION = 483;
 
   /// The number of exception contexts allowed to write. Once this field is
   /// zero, we stop writing any new exception contexts in this process.

pkg/analyzer/lib/src/summary2/ast_binary_tag.dart

@@ -129,18 +129,6 @@ class Tag {
   static const int ParameterKindOptionalPositional = 2;
   static const int ParameterKindRequiredNamed = 3;
   static const int ParameterKindOptionalNamed = 4;
-
-  static const int NullType = 2;
-  static const int DynamicType = 3;
-  static const int FunctionType = 4;
-  static const int InvalidType = 5;
-  static const int NeverType = 6;
-  static const int InterfaceType = 7;
-  static const int InterfaceType_noTypeArguments_none = 8;
-  static const int InterfaceType_noTypeArguments_question = 9;
-  static const int RecordType = 10;
-  static const int TypeParameterType = 11;
-  static const int VoidType = 12;
 }
 
 enum TypeParameterVarianceTag {
@@ -150,3 +138,17 @@ enum TypeParameterVarianceTag {
   contravariant,
   invariant,
 }
+
+enum TypeTag {
+  NullType,
+  DynamicType,
+  FunctionType,
+  InvalidType,
+  NeverType,
+  InterfaceType,
+  InterfaceType_noTypeArguments_none,
+  InterfaceType_noTypeArguments_question,
+  RecordType,
+  TypeParameterType,
+  VoidType,
+}

pkg/analyzer/lib/src/summary2/bundle_reader.dart

@@ -1631,58 +1631,57 @@ class ResolutionReader {
   }
 
   TypeImpl? readType() {
-    var tag = _reader.readByte();
-    if (tag == Tag.NullType) {
-      return null;
-    } else if (tag == Tag.DynamicType) {
-      var type = DynamicTypeImpl.instance;
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.FunctionType) {
-      var type = _readFunctionType();
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.InterfaceType) {
-      var element = readElement() as InterfaceElementImpl;
-      var typeArguments = _readTypeList();
-      var nullability = _readNullability();
-      var type = element.instantiateImpl(
-        typeArguments: typeArguments,
-        nullabilitySuffix: nullability,
-      );
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.InterfaceType_noTypeArguments_none) {
-      var element = readElement() as InterfaceElementImpl;
-      var type = element.instantiateImpl(
-        typeArguments: const [],
-        nullabilitySuffix: NullabilitySuffix.none,
-      );
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.InterfaceType_noTypeArguments_question) {
-      var element = readElement() as InterfaceElementImpl;
-      var type = element.instantiateImpl(
-        typeArguments: const [],
-        nullabilitySuffix: NullabilitySuffix.question,
-      );
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.InvalidType) {
-      var type = InvalidTypeImpl.instance;
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.NeverType) {
-      var nullability = _readNullability();
-      var type = NeverTypeImpl.instance.withNullability(nullability);
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.RecordType) {
-      var type = _readRecordType();
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.TypeParameterType) {
-      var element = readElement() as TypeParameterElementImpl;
-      var nullability = _readNullability();
-      var type = element.instantiate(nullabilitySuffix: nullability);
-      return _readAliasElementArguments(type);
-    } else if (tag == Tag.VoidType) {
-      var type = VoidTypeImpl.instance;
-      return _readAliasElementArguments(type);
-    } else {
-      throw UnimplementedError('$tag');
+    var tag = readEnum(TypeTag.values);
+    switch (tag) {
+      case TypeTag.NullType:
+        return null;
+      case TypeTag.DynamicType:
+        var type = DynamicTypeImpl.instance;
+        return _readAliasElementArguments(type);
+      case TypeTag.FunctionType:
+        var type = _readFunctionType();
+        return _readAliasElementArguments(type);
+      case TypeTag.InterfaceType:
+        var element = readElement() as InterfaceElementImpl;
+        var typeArguments = _readTypeList();
+        var nullability = _readNullability();
+        var type = element.instantiateImpl(
+          typeArguments: typeArguments,
+          nullabilitySuffix: nullability,
+        );
+        return _readAliasElementArguments(type);
+      case TypeTag.InterfaceType_noTypeArguments_none:
+        var element = readElement() as InterfaceElementImpl;
+        var type = element.instantiateImpl(
+          typeArguments: const [],
+          nullabilitySuffix: NullabilitySuffix.none,
+        );
+        return _readAliasElementArguments(type);
+      case TypeTag.InterfaceType_noTypeArguments_question:
+        var element = readElement() as InterfaceElementImpl;
+        var type = element.instantiateImpl(
+          typeArguments: const [],
+          nullabilitySuffix: NullabilitySuffix.question,
+        );
+        return _readAliasElementArguments(type);
+      case TypeTag.InvalidType:
+        var type = InvalidTypeImpl.instance;
+        return _readAliasElementArguments(type);
+      case TypeTag.NeverType:
+        var nullability = _readNullability();
+        var type = NeverTypeImpl.instance.withNullability(nullability);
+        return _readAliasElementArguments(type);
+      case TypeTag.RecordType:
+        var type = _readRecordType();
+        return _readAliasElementArguments(type);
+      case TypeTag.TypeParameterType:
+        var element = readElement() as TypeParameterElementImpl;
+        var nullability = _readNullability();
+        var type = element.instantiate(nullabilitySuffix: nullability);
+        return _readAliasElementArguments(type);
+      case TypeTag.VoidType:
+        var type = VoidTypeImpl.instance;
+        return _readAliasElementArguments(type);
     }
   }
 

pkg/analyzer/lib/src/summary2/bundle_writer.dart

@@ -922,9 +922,9 @@ class ResolutionSink extends _SummaryDataWriter {
 
   void writeType(DartType? type) {
     if (type == null) {
-      writeByte(Tag.NullType);
+      writeEnum(TypeTag.NullType);
     } else if (type is DynamicTypeImpl) {
-      writeByte(Tag.DynamicType);
+      writeEnum(TypeTag.DynamicType);
       _writeTypeAliasElementArguments(type);
     } else if (type is FunctionTypeImpl) {
       _writeFunctionType(type);
@@ -934,14 +934,14 @@ class ResolutionSink extends _SummaryDataWriter {
       var nullabilitySuffix = type.nullabilitySuffix;
       if (typeArguments.isEmpty) {
         if (nullabilitySuffix == NullabilitySuffix.none) {
-          writeByte(Tag.InterfaceType_noTypeArguments_none);
+          writeEnum(TypeTag.InterfaceType_noTypeArguments_none);
         } else if (nullabilitySuffix == NullabilitySuffix.question) {
-          writeByte(Tag.InterfaceType_noTypeArguments_question);
+          writeEnum(TypeTag.InterfaceType_noTypeArguments_question);
         }
         // TODO(scheglov): Write raw
         writeElement(type.element);
       } else {
-        writeByte(Tag.InterfaceType);
+        writeEnum(TypeTag.InterfaceType);
         // TODO(scheglov): Write raw
         writeElement(type.element);
         writeUInt30(typeArguments.length);
@@ -952,22 +952,22 @@ class ResolutionSink extends _SummaryDataWriter {
       }
       _writeTypeAliasElementArguments(type);
     } else if (type is InvalidTypeImpl) {
-      writeByte(Tag.InvalidType);
+      writeEnum(TypeTag.InvalidType);
       _writeTypeAliasElementArguments(type);
     } else if (type is NeverTypeImpl) {
-      writeByte(Tag.NeverType);
+      writeEnum(TypeTag.NeverType);
       _writeNullabilitySuffix(type.nullabilitySuffix);
       _writeTypeAliasElementArguments(type);
     } else if (type is RecordTypeImpl) {
       _writeRecordType(type);
       _writeTypeAliasElementArguments(type);
     } else if (type is TypeParameterTypeImpl) {
-      writeByte(Tag.TypeParameterType);
+      writeEnum(TypeTag.TypeParameterType);
       writeElement(type.element);
       _writeNullabilitySuffix(type.nullabilitySuffix);
       _writeTypeAliasElementArguments(type);
     } else if (type is VoidTypeImpl) {
-      writeByte(Tag.VoidType);
+      writeEnum(TypeTag.VoidType);
       _writeTypeAliasElementArguments(type);
     } else {
       throw UnimplementedError('${type.runtimeType}');
@@ -1026,7 +1026,7 @@ class ResolutionSink extends _SummaryDataWriter {
   void _writeFunctionType(FunctionTypeImpl type) {
     type = _toSyntheticFunctionType(type);
 
-    writeByte(Tag.FunctionType);
+    writeEnum(TypeTag.FunctionType);
 
     _writeTypeParameters(type.typeFormals, () {
       writeType(type.returnType);
@@ -1070,7 +1070,7 @@ class ResolutionSink extends _SummaryDataWriter {
   }
 
   void _writeRecordType(RecordTypeImpl type) {
-    writeByte(Tag.RecordType);
+    writeEnum(TypeTag.RecordType);
 
     writeList<RecordTypePositionalField>(type.positionalFields, (field) {
       writeType(field.type);