[DAS] Fixes writeType importing shadowed type by local declaration

Fixes: #59701
Change-Id: Ief2816ee8b05296adfdbb4f2c1f01a8892711136
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/451404
Auto-Submit: Felipe Morschel <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: FMorschel

pkg/analysis_server/test/src/services/correction/assist/add_type_annotation_test.dart

@@ -483,11 +483,9 @@ void f(int Function(int) p) {
   v = p;
 }
 ''');
-    // TODO(brianwilkerson): Improve `DartChangeBuilder.writeType` so that
-    //  unnecessary parameter names (`p1`) are not written.
     await assertHasAssist('''
 void f(int Function(int) p) {
-  int Function(int p1) v;
+  int Function(int) v;
   v = p;
 }
 ''');
@@ -678,6 +676,34 @@ void f() {
 ''');
   }
 
+  Future<void> test_local_shadowed() async {
+    newFile(join(testPackageLibPath, 'a.dart'), '''
+class A {}
+''');
+    newFile(join(testPackageLibPath, 'other.dart'), '''
+import 'a.dart';
+A getA() => A();
+''');
+    await resolveTestCode('''
+import 'other.dart';
+
+class A {}
+void f() {
+  var ^v = getA();
+}
+''');
+    await assertHasAssist('''
+import 'package:test/a.dart' as prefix0;
+
+import 'other.dart';
+
+class A {}
+void f() {
+  prefix0.A v = getA();
+}
+''');
+  }
+
   Future<void> test_local_unknown() async {
     verifyNoTestUnitErrors = false;
     await resolveTestCode('''

pkg/analysis_server/test/src/services/correction/fix/add_type_annotation_test.dart

@@ -208,7 +208,7 @@ f() {
   switch (A(1)) {
     case A(a: >0 && final b): print(b);
   }
- }
+}
 ''');
     await assertHasFix('''
 class A {
@@ -219,7 +219,7 @@ f() {
   switch (A(1)) {
     case A(a: >0 && final int b): print(b);
   }
- }
+}
 ''');
   }
 

pkg/analysis_server/test/src/services/correction/fix/convert_to_function_declaration_test.dart

@@ -156,7 +156,7 @@ void f() {
 ''');
     await assertHasFix('''
 void f() {
-  int v1(int Function(String p1)? p) {
+  int v1(int Function(String)? p) {
     return p?.call('') ?? 0;
   }
   v1((s) => 0);

pkg/analyzer_plugin/api.txt

@@ -1731,7 +1731,7 @@ package:analyzer_plugin/utilities/change_builder/change_builder_dart.dart:
     writeConstructorDeclaration (method: void Function(String, {ArgumentList? argumentList, void Function()? bodyWriter, String? classNameGroupName, String? constructorName, String? constructorNameGroupName, List<String>? fieldNames, void Function()? initializerWriter, bool isConst, void Function()? parameterWriter}))
     writeFieldDeclaration (method: void Function(String, {void Function()? initializerWriter, bool isConst, bool isFinal, bool isStatic, String? nameGroupName, DartType? type, String? typeGroupName}))
     writeFormalParameter (method: void Function(String, {bool isCovariant, bool isRequiredNamed, bool isRequiredType, deprecated ExecutableElement? methodBeingCopied, String? nameGroupName, DartType? type, String? typeGroupName, List<TypeParameterElement>? typeParametersInScope}))
-    writeFormalParameters (method: void Function(Iterable<FormalParameterElement>, {String? groupNamePrefix, bool includeDefaultValues, deprecated ExecutableElement? methodBeingCopied, bool requiredTypes, List<TypeParameterElement>? typeParametersInScope}))
+    writeFormalParameters (method: void Function(Iterable<FormalParameterElement>, {bool fillParameterNames, String? groupNamePrefix, bool includeDefaultValues, deprecated ExecutableElement? methodBeingCopied, bool requiredTypes, List<TypeParameterElement>? typeParametersInScope}))
     writeFunctionDeclaration (method: void Function(String, {void Function()? bodyWriter, bool isStatic, String? nameGroupName, void Function()? parameterWriter, DartType? returnType, String? returnTypeGroupName}))
     writeGetterDeclaration (method: void Function(String, {void Function() bodyWriter, bool isStatic, String nameGroupName, DartType returnType, String returnTypeGroupName}))
     writeImportedName (method: void Function(List<Uri>, String))

pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart

@@ -333,6 +333,7 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
     ExecutableElement? methodBeingCopied,
     List<TypeParameterElement>? typeParametersInScope,
     String? groupNamePrefix,
+    bool fillParameterNames = true,
     bool includeDefaultValues = true,
     bool requiredTypes = false,
   }) {
@@ -364,13 +365,13 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
       }
       // Parameter.
       var name = parameter.name;
-      if (name == null || name == '') {
-        name = _generateUniqueName(parameterNames, 'p');
+      if ((name == null || name == '') && fillParameterNames) {
+        name = _generateUniqueName(parameterNames);
         parameterNames.add(name);
       }
       var groupPrefix = groupNamePrefix != null ? '$groupNamePrefix:' : '';
       writeFormalParameter(
-        name,
+        name ?? '',
         isCovariant: parameter.isCovariant,
         isRequiredNamed: parameter.isRequiredNamed,
         typeParametersInScope: typeParametersInScope,
@@ -1191,7 +1192,7 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
 
   /// Generates a name that does not occur in [existingNames] that begins with
   /// the given [prefix].
-  String _generateUniqueName(Set<String> existingNames, String prefix) {
+  String _generateUniqueName(Set<String> existingNames, {String prefix = 'p'}) {
     var index = 1;
     var name = '$prefix$index';
     while (existingNames.contains(name)) {
@@ -1459,7 +1460,16 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
     if (import == null) {
       var library = element.library?.uri;
       if (library != null) {
-        import = _dartFileEditBuilder._importLibrary(library);
+        var shadowed =
+            _dartFileEditBuilder.resolvedLibrary.element.publicNamespace.get2(
+              element.displayName,
+            ) !=
+            null;
+        String? prefix;
+        if (shadowed) {
+          prefix = _dartFileEditBuilder._defaultImportPrefixFor(library);
+        }
+        import = _dartFileEditBuilder._importLibrary(library, prefix: prefix);
       }
     }
     if (import == null) {
@@ -1561,6 +1571,7 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
         type.formalParameters,
         typeParametersInScope: typeParametersInScope,
         includeDefaultValues: false,
+        fillParameterNames: false,
       );
       if (type.nullabilitySuffix == NullabilitySuffix.question) {
         write('?');
@@ -2606,6 +2617,33 @@ class DartFileEditBuilderImpl extends FileEditBuilderImpl
     }, insertBeforeExisting: true);
   }
 
+  String _defaultImportPrefixFor(Uri uri) {
+    if (importPrefixGenerator != null) {
+      return importPrefixGenerator!(uri);
+    }
+    // TODO(FMorschel): Think of a way to identify if the current editing range
+    // already contains a variable with the same name as the generated prefix.
+    // This only accounts for top-level names.
+    var existingNames = {
+      ...resolvedLibrary.element.exportNamespace.definedNames2.keys,
+    };
+    for (var unit in resolvedLibrary.units) {
+      existingNames.addAll(
+        unit.unit.directives
+            .whereType<ImportDirective>()
+            .map((d) => d.prefix?.name)
+            .nonNulls,
+      );
+    }
+    var suffix = 0;
+    var prefix = 'prefix$suffix';
+    while (existingNames.contains(prefix)) {
+      suffix++;
+      prefix = 'prefix$suffix';
+    }
+    return prefix;
+  }
+
   /// Returns information about the library used to import the given [element]
   /// into the target library, or `null` if the element was not imported, such
   /// as when the element is declared in the same library.

pkg/analyzer_plugin/lib/utilities/change_builder/change_builder_dart.dart

@@ -185,6 +185,7 @@ abstract class DartEditBuilder implements EditBuilder {
     ExecutableElement? methodBeingCopied,
     List<TypeParameterElement>? typeParametersInScope,
     String? groupNamePrefix,
+    bool fillParameterNames = true,
     bool includeDefaultValues = true,
     bool requiredTypes,
   });