Use unifying type visitor instead of custom logic

drift_dev/lib/src/analysis/results/dart.dart

@@ -4,6 +4,7 @@ import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/dart/element/type_visitor.dart';
 import 'package:build/build.dart';
 import 'package:json_annotation/json_annotation.dart';
 
@@ -115,7 +116,7 @@ class AnnotatedDartCodeBuilder {
   }
 
   void addDartType(DartType type) {
-    _AddFromDartType(this).writeType(type);
+    type.accept(_AddFromDartType(this));
   }
 
   void addAstNode(AstNode node, {Set<AstNode> exclude = const {}}) {
@@ -244,9 +245,7 @@ class DartTopLevelSymbol {
 ///
 /// This representation allwos emitting the Dart type with relevant imports
 /// managed dynamically.
-// Note: We don't extend TypeVisitor because we're not supposed to and the
+class _AddFromDartType extends UnifyingTypeVisitor<void> {
-// inteface doesn't appear to be stable.
-class _AddFromDartType {
   final AnnotatedDartCodeBuilder _builder;
 
   _AddFromDartType(this._builder);
@@ -264,29 +263,15 @@ class _AddFromDartType {
     }
   }
 
-  void writeType(DartType type) {
+  @override
-    if (type is DynamicType) {
+  void visitDartType(DartType type) {
-      visitDynamicType(type);
+    _builder
-    } else if (type is FunctionType) {
+      ..addText('dynamic')
-      visitFunctionType(type);
+      ..addText(
-    } else if (type is InterfaceType) {
+          '/* unhandled ${type.getDisplayString(withNullability: true)} */');
-      visitInterfaceType(type);
-    } else if (type is InvalidType) {
-      visitInvalidType(type);
-    } else if (type is NeverType) {
-      visitNeverType(type);
-    } else if (type is RecordType) {
-      visitRecordType(type);
-    } else if (type is TypeParameterType) {
-      visitTypeParameterType(type);
-    } else if (type is VoidType) {
-      visitVoidType(type);
-    } else {
-      _builder.addText(
-          '/* unknown type ${type.getDisplayString(withNullability: true)} */');
-    }
   }
 
+  @override
   void visitRecordType(RecordType type) {
     _builder.addText('(');
     var first = true;
@@ -297,7 +282,7 @@ class _AddFromDartType {
       }
       first = false;
 
-      writeType(field.type);
+      field.type.accept(this);
     }
 
     if (type.namedFields.isNotEmpty) {
@@ -309,7 +294,7 @@ class _AddFromDartType {
         }
         first = false;
 
-        writeType(field.type);
+        field.type.accept(this);
         _builder
           ..addText(' ')
           ..addText(field.name);
@@ -321,12 +306,14 @@ class _AddFromDartType {
     _writeSuffix(type.nullabilitySuffix);
   }
 
+  @override
   void visitDynamicType(DynamicType type) {
     _builder.addText('dynamic');
   }
 
+  @override
   void visitFunctionType(FunctionType type) {
-    writeType(type.returnType);
+    type.returnType.accept(this);
 
     _builder.addText(' Function');
     final formals = type.typeFormals;
@@ -342,7 +329,7 @@ class _AddFromDartType {
         final bound = arg.bound;
         if (bound != null) {
           _builder.addText(' extends ');
-          writeType(bound);
+          bound.accept(this);
         }
         i++;
       }
@@ -374,7 +361,7 @@ class _AddFromDartType {
         _builder.addText(', ');
       }
 
-      writeType(parameter.type);
+      parameter.type.accept(this);
       if (parameter.isNamed) {
         _builder.addText(' ${parameter.name}');
       }
@@ -389,6 +376,7 @@ class _AddFromDartType {
     _writeSuffix(type.nullabilitySuffix);
   }
 
+  @override
   void visitInterfaceType(InterfaceType type) {
     final alias = type.alias;
     if (alias != null) {
@@ -405,7 +393,7 @@ class _AddFromDartType {
           _builder.addText(', ');
         }
 
-        writeType(arg);
+        arg.accept(this);
         i++;
       }
       _builder.addText('>');
@@ -414,22 +402,26 @@ class _AddFromDartType {
     _writeSuffix(type.nullabilitySuffix);
   }
 
+  @override
   void visitInvalidType(InvalidType type) {
     _builder
       ..addText('dynamic')
       ..addText('/* = invalid*/');
   }
 
+  @override
   void visitNeverType(NeverType type) {
     _builder.addText('Never');
     _writeSuffix(type.nullabilitySuffix);
   }
 
+  @override
   void visitTypeParameterType(TypeParameterType type) {
     _builder.addText(type.element.name);
     _writeSuffix(type.nullabilitySuffix);
   }
 
+  @override
   void visitVoidType(VoidType type) {
     _builder.addText('void');
     _writeSuffix(type.nullabilitySuffix);