Migrate the first round of completion support

Change-Id: I64ca0b7b6d3040b6e37d328ed62e75059c48ef07 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/194212 Reviewed-by: Konstantin Shcheglov <scheglov@google.com> Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
2021-04-07 20:44:58 +00:00
parent f4a9cad199
commit a0f7ff92a1
17 changed files with 190 additions and 212 deletions
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ -52,7 +50,7 @@ abstract class CompletionRequest {

  /// Return the content of the [source] in which the completion is being
  /// requested, or `null` if the content could not be accessed.
-  String get sourceContents;
+  String? get sourceContents;

  /// Throw [AbortCompletion] if the completion request has been aborted.
  void checkAborted();
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/provisional/completion/completion_core.dart';
 import 'package:analysis_server/src/services/completion/completion_performance.dart';
 import 'package:analyzer/dart/analysis/results.dart';
@@ -46,10 +44,10 @@ class CompletionRequestImpl implements CompletionRequest {
  ResourceProvider get resourceProvider => result.session.resourceProvider;

  @override
-  Source get source => result.unit.declaredElement.source;
+  Source get source => result.unit!.declaredElement!.source;

  @override
-  String get sourceContents => result?.content;
+  String? get sourceContents => result.content;

  /// Abort the current completion request.
  void abort() {
@@ -2,19 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analyzer/src/util/performance/operation_performance.dart';

 /// Compute a string representing a code completion operation at the
 /// given source and location.
 ///
 /// This string is useful for displaying to users in a diagnostic context.
-String computeCompletionSnippet(String contents, int offset) {
-  if (contents == null ||
-      offset == null ||
-      offset < 0 ||
-      contents.length < offset) {
+String _computeCompletionSnippet(String contents, int offset) {
+  if (offset < 0 || contents.length < offset) {
    return '???';
  }
  var start = offset;
@@ -40,13 +35,17 @@ String computeCompletionSnippet(String contents, int offset) {

 /// Overall performance of a code completion operation.
 class CompletionPerformance {
-  String path;
+  String? path;
  String snippet = '';
  int suggestionCount = -1;
-  OperationPerformanceImpl _operation;
+  OperationPerformance? _operation;

  int get elapsedInMilliseconds {
-    return _operation.elapsed.inMilliseconds;
+    var operation = _operation;
+    if (operation == null) {
+      throw StateError('Access of elapsed time before the operation is run');
+    }
+    return operation.elapsed.inMilliseconds;
  }

  String get suggestionCountStr {
@@ -68,6 +67,6 @@ class CompletionPerformance {
  }

  void setContentsAndOffset(String contents, int offset) {
-    snippet = computeCompletionSnippet(contents, offset);
+    snippet = _computeCompletionSnippet(contents, offset);
  }
 }
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 /// Utility methods to compute the value of the features used for code
 /// completion.
 import 'dart:math' as math;
@@ -46,27 +44,6 @@ const List<String> stringNames = [
  'string'
 ];

-DartType impliedDartTypeWithName(TypeProvider typeProvider, String name) {
-  if (typeProvider == null || name == null || name.isEmpty) {
-    return null;
-  }
-  if (intNames.contains(name)) {
-    return typeProvider.intType;
-  } else if (numNames.contains(name)) {
-    return typeProvider.numType;
-  } else if (listNames.contains(name)) {
-    return typeProvider.listType(typeProvider.dynamicType);
-  } else if (stringNames.contains(name)) {
-    return typeProvider.stringType;
-  } else if (name == 'iterator') {
-    return typeProvider.iterableDynamicType;
-  } else if (name == 'map') {
-    return typeProvider.mapType(
-        typeProvider.dynamicType, typeProvider.dynamicType);
-  }
-  return null;
-}
-
 /// Convert a relevance score (assumed to be between `0.0` and `1.0` inclusive)
 /// to a relevance value between `0` and `1000`.
 int toRelevance(double score) {
@@ -106,6 +83,27 @@ double weightedAverage(
  return (average + 1.0) / 2.0;
 }

+DartType? _impliedDartTypeWithName(TypeProvider typeProvider, String name) {
+  if (name.isEmpty) {
+    return null;
+  }
+  if (intNames.contains(name)) {
+    return typeProvider.intType;
+  } else if (numNames.contains(name)) {
+    return typeProvider.numType;
+  } else if (listNames.contains(name)) {
+    return typeProvider.listType(typeProvider.dynamicType);
+  } else if (stringNames.contains(name)) {
+    return typeProvider.stringType;
+  } else if (name == 'iterator') {
+    return typeProvider.iterableDynamicType;
+  } else if (name == 'map') {
+    return typeProvider.mapType(
+        typeProvider.dynamicType, typeProvider.dynamicType);
+  }
+  return null;
+}
+
 /// Return the weighted average of the given [values], applying the given
 /// [weights]. The number of weights must be equal to the number of values.
 double _weightedAverage(List<double> values, List<double> weights) {
@@ -165,7 +163,7 @@ class FeatureComputer {
  /// Return the type imposed when completing at the given [offset], where the
  /// offset is within the given [node], or `null` if the context does not
  /// impose any type.
-  DartType computeContextType(AstNode node, int offset) {
+  DartType? computeContextType(AstNode node, int offset) {
    var type = node
        .accept(_ContextTypeVisitor(typeProvider, offset))
        ?.resolveToBound(typeProvider.objectType);
@@ -193,7 +191,7 @@ class FeatureComputer {
    } else if (element is FieldElement && element.isEnumConstant) {
      return protocol.ElementKind.ENUM_CONSTANT;
    } else if (element is PropertyAccessorElement) {
-      element = (element as PropertyAccessorElement).variable;
+      element = element.variable;
    }
    var kind = element.kind;
    if (kind == ElementKind.CONSTRUCTOR) {
@@ -229,7 +227,7 @@ class FeatureComputer {
  /// Return the value of the _context type_ feature for an element with the
  /// given [elementType] when completing in a location with the given
  /// [contextType].
-  double contextTypeFeature(DartType contextType, DartType elementType) {
+  double contextTypeFeature(DartType? contextType, DartType? elementType) {
    if (contextType == null || elementType == null) {
      // Disable the feature if we don't have both types.
      return 0.0;
@@ -252,8 +250,8 @@ class FeatureComputer {
  /// Return the value of the _element kind_ feature for the [element] when
  /// completing at the given [completionLocation]. If a [distance] is given it
  /// will be used to provide finer-grained relevance scores.
-  double elementKindFeature(Element element, String completionLocation,
-      {double distance}) {
+  double elementKindFeature(Element element, String? completionLocation,
+      {double? distance}) {
    if (completionLocation == null) {
      return 0.0;
    }
@@ -327,7 +325,7 @@ class FeatureComputer {

  /// Return the value of the _keyword_ feature for the [keyword] when
  /// completing at the given [completionLocation].
-  double keywordFeature(String keyword, String completionLocation) {
+  double keywordFeature(String keyword, String? completionLocation) {
    if (completionLocation == null) {
      return 0.0;
    }
@@ -357,7 +355,7 @@ class FeatureComputer {
  /// declarations between the local variable and the reference.
  int localVariableDistance(AstNode reference, LocalVariableElement variable) {
    var distance = 0;
-    var node = reference;
+    AstNode? node = reference;
    while (node != null) {
      if (node is ForStatement || node is ForElement) {
        var loopParts = node is ForStatement
@@ -440,7 +438,7 @@ class FeatureComputer {

  /// Return the value of the _super matches_ feature.
  double superMatchesFeature(
-          String containingMethodName, String proposedMemberName) =>
+          String? containingMethodName, String proposedMemberName) =>
      containingMethodName == null
          ? 0.0
          : (proposedMemberName == containingMethodName ? 1.0 : 0.0);
@@ -451,7 +449,7 @@ class FeatureComputer {
    if (distance < 0) {
      return 0.0;
    }
-    return math.pow(0.9, distance);
+    return math.pow(0.9, distance) as double;
  }

  /// Return the inheritance distance between the [subclass] and the
@@ -459,7 +457,7 @@ class FeatureComputer {
  /// cycles in the type graph.
  ///
  /// This is the implementation of [inheritanceDistance].
-  int _inheritanceDistance(ClassElement subclass, ClassElement superclass,
+  int _inheritanceDistance(ClassElement? subclass, ClassElement superclass,
      Set<ClassElement> visited) {
    if (subclass == null) {
      return -1;
@@ -504,7 +502,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  _ContextTypeVisitor(this.typeProvider, this.offset);

  @override
-  DartType visitAdjacentStrings(AdjacentStrings node) {
+  DartType? visitAdjacentStrings(AdjacentStrings node) {
    if (offset == node.offset) {
      return _visitParent(node);
    }
@@ -512,7 +510,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitArgumentList(ArgumentList node) {
+  DartType? visitArgumentList(ArgumentList node) {
    if (range
        .endStart(node.leftParenthesis, node.rightParenthesis)
        .contains(offset)) {
@@ -523,7 +521,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {

      var index = 0;

-      DartType typeOfIndexPositionalParameter() {
+      DartType? typeOfIndexPositionalParameter() {
        if (index < parameters.length) {
          var parameter = parameters[index];
          if (parameter.isPositional) {
@@ -533,7 +531,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
        return null;
      }

-      Expression previousArgument;
+      Expression? previousArgument;
      for (var argument in node.arguments) {
        if (argument is NamedExpression) {
          if (offset <= argument.offset) {
@@ -560,7 +558,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitAsExpression(AsExpression node) {
+  DartType? visitAsExpression(AsExpression node) {
    if (node.asOperator.end < offset) {
      return node.expression.staticType;
    }
@@ -568,10 +566,10 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitAssertInitializer(AssertInitializer node) {
+  DartType? visitAssertInitializer(AssertInitializer node) {
    if (range
        .endStart(node.leftParenthesis,
-            node.message?.beginToken?.previous ?? node.rightParenthesis)
+            node.message?.beginToken.previous ?? node.rightParenthesis)
        .contains(offset)) {
      return typeProvider.boolType;
    }
@@ -579,10 +577,10 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitAssertStatement(AssertStatement node) {
+  DartType? visitAssertStatement(AssertStatement node) {
    if (range
        .endStart(node.leftParenthesis,
-            node.message?.beginToken?.previous ?? node.rightParenthesis)
+            node.message?.beginToken.previous ?? node.rightParenthesis)
        .contains(offset)) {
      return typeProvider.boolType;
    }
@@ -590,7 +588,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitAssignmentExpression(AssignmentExpression node) {
+  DartType? visitAssignmentExpression(AssignmentExpression node) {
    if (node.operator.end <= offset) {
      // RHS
      if (node.operator.type == TokenType.EQ) {
@@ -599,7 +597,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
      var method = node.staticElement;
      if (method != null) {
        var parameters = method.parameters;
-        if (parameters != null && parameters.isNotEmpty) {
+        if (parameters.isNotEmpty) {
          return parameters[0].type;
        }
      }
@@ -608,12 +606,12 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitAwaitExpression(AwaitExpression node) {
+  DartType? visitAwaitExpression(AwaitExpression node) {
    return _visitParent(node);
  }

  @override
-  DartType visitBinaryExpression(BinaryExpression node) {
+  DartType? visitBinaryExpression(BinaryExpression node) {
    if (node.operator.end <= offset) {
      return node.rightOperand.staticParameterElement?.type;
    }
@@ -621,15 +619,15 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitCascadeExpression(CascadeExpression node) {
-    if (node.target != null && offset == node.target.offset) {
+  DartType? visitCascadeExpression(CascadeExpression node) {
+    if (offset == node.target.offset) {
      return _visitParent(node);
    }
    return null;
  }

  @override
-  DartType visitConditionalExpression(ConditionalExpression node) {
+  DartType? visitConditionalExpression(ConditionalExpression node) {
    if (offset <= node.question.offset) {
      return typeProvider.boolType;
    } else {
@@ -638,8 +636,8 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitConstructorFieldInitializer(ConstructorFieldInitializer node) {
-    if (node.equals != null && node.equals.end <= offset) {
+  DartType? visitConstructorFieldInitializer(ConstructorFieldInitializer node) {
+    if (node.equals.end <= offset) {
      var element = node.fieldName.staticElement;
      if (element is FieldElement) {
        return element.type;
@@ -649,15 +647,16 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitDefaultFormalParameter(DefaultFormalParameter node) {
-    if (node.separator != null && node.separator.end <= offset) {
-      return node.parameter.declaredElement.type;
+  DartType? visitDefaultFormalParameter(DefaultFormalParameter node) {
+    var separator = node.separator;
+    if (separator != null && separator.end <= offset) {
+      return node.parameter.declaredElement?.type;
    }
    return null;
  }

  @override
-  DartType visitDoStatement(DoStatement node) {
+  DartType? visitDoStatement(DoStatement node) {
    if (range
        .endStart(node.leftParenthesis, node.rightParenthesis)
        .contains(offset)) {
@@ -667,7 +666,7 @@ class _ContextTypeVisitor extends SimpleAstVisitor<DartType> {
  }

  @override
-  DartType visitExpressionFunctionBody(ExpressionFunctionBody node) {
+  DartType? visitExpressionFunctionBody(ExpressionFunctionBody node) {
    if (range.endEnd(node.functionDefinition, node).contains(offset)) {
      var parent = node.parent;
      if (parent is MethodDeclaration) {
@@ -684,7 +683,7 @@ Class: ${parent.parent}
      } else if (parent is FunctionExpression) {
        var grandparent = parent.parent;
        if (grandparent is FunctionDeclaration) {
-          return BodyInferenceContext.of(parent.body).contextType;
+          return BodyInferenceContext.of(parent.body)?.contextType;
        }
        return _visitParent(parent);
      }
@@ -693,15 +692,15 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitFieldDeclaration(FieldDeclaration node) {
-    if (node.fields != null && node.fields.contains(offset)) {
+  DartType? visitFieldDeclaration(FieldDeclaration node) {
+    if (node.fields.contains(offset)) {
      return node.fields.accept(this);
    }
    return null;
  }

  @override
-  DartType visitForEachPartsWithDeclaration(ForEachPartsWithDeclaration node) {
+  DartType? visitForEachPartsWithDeclaration(ForEachPartsWithDeclaration node) {
    if (range
        .startOffsetEndOffset(node.inKeyword.end, node.end)
        .contains(offset)) {
@@ -716,7 +715,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitForEachPartsWithIdentifier(ForEachPartsWithIdentifier node) {
+  DartType? visitForEachPartsWithIdentifier(ForEachPartsWithIdentifier node) {
    if (range.endEnd(node.inKeyword, node).contains(offset)) {
      var parent = node.parent;
      if ((parent is ForStatement && parent.awaitKeyword != null) ||
@@ -729,31 +728,27 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitForPartsWithDeclarations(ForPartsWithDeclarations node) {
-    if (node.leftSeparator != null &&
-        node.rightSeparator != null &&
-        range
-            .endStart(node.leftSeparator, node.rightSeparator)
-            .contains(offset)) {
+  DartType? visitForPartsWithDeclarations(ForPartsWithDeclarations node) {
+    if (range
+        .endStart(node.leftSeparator, node.rightSeparator)
+        .contains(offset)) {
      return typeProvider.boolType;
    }
    return null;
  }

  @override
-  DartType visitForPartsWithExpression(ForPartsWithExpression node) {
-    if (node.leftSeparator != null &&
-        node.rightSeparator != null &&
-        range
-            .endStart(node.leftSeparator, node.rightSeparator)
-            .contains(offset)) {
+  DartType? visitForPartsWithExpression(ForPartsWithExpression node) {
+    if (range
+        .endStart(node.leftSeparator, node.rightSeparator)
+        .contains(offset)) {
      return typeProvider.boolType;
    }
    return null;
  }

  @override
-  DartType visitFunctionExpressionInvocation(
+  DartType? visitFunctionExpressionInvocation(
      FunctionExpressionInvocation node) {
    if (node.function.contains(offset)) {
      return _visitParent(node);
@@ -762,7 +757,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitIfElement(IfElement node) {
+  DartType? visitIfElement(IfElement node) {
    if (range
        .endStart(node.leftParenthesis, node.rightParenthesis)
        .contains(offset)) {
@@ -772,7 +767,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitIfStatement(IfStatement node) {
+  DartType? visitIfStatement(IfStatement node) {
    if (range
        .endStart(node.leftParenthesis, node.rightParenthesis)
        .contains(offset)) {
@@ -782,7 +777,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitIndexExpression(IndexExpression node) {
+  DartType? visitIndexExpression(IndexExpression node) {
    if (range.endStart(node.leftBracket, node.rightBracket).contains(offset)) {
      var parameters = node.staticElement?.parameters;
      if (parameters != null && parameters.isNotEmpty) {
@@ -793,7 +788,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitIsExpression(IsExpression node) {
+  DartType? visitIsExpression(IsExpression node) {
    if (node.isOperator.end < offset) {
      return node.expression.staticType;
    }
@@ -801,7 +796,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitLabel(Label node) {
+  DartType? visitLabel(Label node) {
    if (offset == node.offset) {
      return _visitParent(node);
    }
@@ -812,7 +807,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitListLiteral(ListLiteral node) {
+  DartType? visitListLiteral(ListLiteral node) {
    if (range.endStart(node.leftBracket, node.rightBracket).contains(offset)) {
      return (node.staticType as InterfaceType).typeArguments[0];
    }
@@ -820,10 +815,11 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitMapLiteralEntry(MapLiteralEntry node) {
+  DartType? visitMapLiteralEntry(MapLiteralEntry node) {
    var literal = node.thisOrAncestorOfType<SetOrMapLiteral>();
-    if (literal != null && literal.staticType.isDartCoreMap) {
-      var typeArguments = (literal.staticType as InterfaceType).typeArguments;
+    var literalType = literal?.staticType;
+    if (literalType is InterfaceType && literalType.isDartCoreMap) {
+      var typeArguments = literalType.typeArguments;
      if (offset <= node.separator.offset) {
        return typeArguments[0];
      } else {
@@ -834,7 +830,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitMethodInvocation(MethodInvocation node) {
+  DartType? visitMethodInvocation(MethodInvocation node) {
    if (offset == node.offset) {
      return _visitParent(node);
    }
@@ -842,7 +838,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitNamedExpression(NamedExpression node) {
+  DartType? visitNamedExpression(NamedExpression node) {
    if (offset == node.offset) {
      return _visitParent(node);
    }
@@ -853,65 +849,66 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitParenthesizedExpression(ParenthesizedExpression node) {
+  DartType? visitParenthesizedExpression(ParenthesizedExpression node) {
    return _visitParent(node);
  }

  @override
-  DartType visitPostfixExpression(PostfixExpression node) {
+  DartType? visitPostfixExpression(PostfixExpression node) {
    return node.operand.staticParameterElement?.type;
  }

  @override
-  DartType visitPrefixedIdentifier(PrefixedIdentifier node) {
+  DartType? visitPrefixedIdentifier(PrefixedIdentifier node) {
    return _visitParent(node);
  }

  @override
-  DartType visitPrefixExpression(PrefixExpression node) {
+  DartType? visitPrefixExpression(PrefixExpression node) {
    return node.operand.staticParameterElement?.type;
  }

  @override
-  DartType visitPropertyAccess(PropertyAccess node) {
+  DartType? visitPropertyAccess(PropertyAccess node) {
    return _visitParent(node);
  }

  @override
-  DartType visitReturnStatement(ReturnStatement node) {
+  DartType? visitReturnStatement(ReturnStatement node) {
    if (node.returnKeyword.end < offset) {
      var functionBody = node.thisOrAncestorOfType<FunctionBody>();
      if (functionBody != null) {
-        return BodyInferenceContext.of(functionBody).contextType;
+        return BodyInferenceContext.of(functionBody)?.contextType;
      }
    }
    return null;
  }

  @override
-  DartType visitSetOrMapLiteral(SetOrMapLiteral node) {
+  DartType? visitSetOrMapLiteral(SetOrMapLiteral node) {
    var type = node.staticType;
-    if (range.endStart(node.leftBracket, node.rightBracket).contains(offset) &&
+    if (type is InterfaceType &&
+        range.endStart(node.leftBracket, node.rightBracket).contains(offset) &&
        (type.isDartCoreMap || type.isDartCoreSet)) {
-      return (type as InterfaceType).typeArguments[0];
+      return type.typeArguments[0];
    }
    return null;
  }

  @override
-  DartType visitSimpleIdentifier(SimpleIdentifier node) {
+  DartType? visitSimpleIdentifier(SimpleIdentifier node) {
    return _visitParent(node);
  }

  @override
-  DartType visitSimpleStringLiteral(SimpleStringLiteral node) {
+  DartType? visitSimpleStringLiteral(SimpleStringLiteral node) {
    // The only completion inside of a String literal would be a directive,
    // where the context type would not be of value.
    return null;
  }

  @override
-  DartType visitSpreadElement(SpreadElement node) {
+  DartType? visitSpreadElement(SpreadElement node) {
    if (node.spreadOperator.end <= offset) {
      var currentNode = node.parent;
      while (currentNode != null) {
@@ -931,44 +928,45 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitSwitchCase(SwitchCase node) {
+  DartType? visitSwitchCase(SwitchCase node) {
    if (range.endStart(node.keyword, node.colon).contains(offset)) {
      var parent = node.parent;
      if (parent is SwitchStatement) {
-        return parent.expression?.staticType;
+        return parent.expression.staticType;
      }
    }
    return super.visitSwitchCase(node);
  }

  @override
-  DartType visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
-    if (node.variables != null && node.variables.contains(offset)) {
+  DartType? visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
+    if (node.variables.contains(offset)) {
      return node.variables.accept(this);
    }
    return null;
  }

  @override
-  DartType visitVariableDeclaration(VariableDeclaration node) {
-    if (node.equals != null && node.equals.end <= offset) {
+  DartType? visitVariableDeclaration(VariableDeclaration node) {
+    var equals = node.equals;
+    if (equals != null && equals.end <= offset) {
      var parent = node.parent;
      if (parent is VariableDeclarationList) {
        return parent.type?.type ??
-            impliedDartTypeWithName(typeProvider, node.name?.name);
+            _impliedDartTypeWithName(typeProvider, node.name.name);
      }
    }
    return null;
  }

  @override
-  DartType visitVariableDeclarationList(VariableDeclarationList node) {
+  DartType? visitVariableDeclarationList(VariableDeclarationList node) {
    for (var varDecl in node.variables) {
-      if (varDecl != null && varDecl.contains(offset)) {
+      if (varDecl.contains(offset)) {
        var equals = varDecl.equals;
        if (equals != null && equals.end <= offset) {
          return node.type?.type ??
-              impliedDartTypeWithName(typeProvider, varDecl.name?.name);
+              _impliedDartTypeWithName(typeProvider, varDecl.name.name);
        }
      }
    }
@@ -976,7 +974,7 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitWhileStatement(WhileStatement node) {
+  DartType? visitWhileStatement(WhileStatement node) {
    if (range
        .endStart(node.leftParenthesis, node.rightParenthesis)
        .contains(offset)) {
@@ -986,11 +984,11 @@ Class: ${parent.parent}
  }

  @override
-  DartType visitYieldStatement(YieldStatement node) {
+  DartType? visitYieldStatement(YieldStatement node) {
    if (range.endStart(node.yieldKeyword, node.semicolon).contains(offset)) {
      var functionBody = node.thisOrAncestorOfType<FunctionBody>();
      if (functionBody != null) {
-        return BodyInferenceContext.of(functionBody).contextType;
+        return BodyInferenceContext.of(functionBody)?.contextType;
      }
    }
    return null;
@@ -999,7 +997,7 @@ Class: ${parent.parent}
  /// Return the result of visiting the parent of the [node] after setting the
  /// [childNode] to the [node]. Note that this method is destructive in that it
  /// does not reset the [childNode] before returning.
-  DartType _visitParent(AstNode node) {
+  DartType? _visitParent(AstNode node) {
    var parent = node.parent;
    if (parent == null) {
      return null;
@@ -1016,7 +1014,7 @@ extension on AstNode {
 /// Some useful extensions on [ArgumentList] for this computer.
 extension on ArgumentList {
  /// Return the [FunctionType], if there is one, for this [ArgumentList].
-  FunctionType get functionType {
+  FunctionType? get functionType {
    var parent = this.parent;
    if (parent is InstanceCreationExpression) {
      return parent.constructorName.staticElement?.type;
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/services/completion/yaml/producer.dart';
 import 'package:analysis_server/src/services/completion/yaml/yaml_completion_generator.dart';
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/services/completion/yaml/producer.dart';
 import 'package:analysis_server/src/services/completion/yaml/yaml_completion_generator.dart';
 import 'package:analyzer/file_system/file_system.dart';
@@ -2,12 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/services/pub/pub_package_service.dart';
 import 'package:analyzer/file_system/file_system.dart';
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;

 /// An object that represents the location of a Boolean value.
@@ -117,8 +114,9 @@ abstract class KeyValueProducer extends Producer {
  /// Initialize a producer representing a key/value pair in a map.
  const KeyValueProducer();

-  /// Returns a producer for values of the given [key].
-  Producer producerForKey(String key);
+  /// Returns a producer for values of the given [key], or `null` if there is
+  /// no registered producer for the [key].
+  Producer? producerForKey(String key);
 }

 /// An object that represents the location of an element in a list.
@@ -155,7 +153,7 @@ class MapProducer extends KeyValueProducer {
  const MapProducer(this._children);

  @override
-  Producer producerForKey(String key) => _children[key];
+  Producer? producerForKey(String key) => _children[key];

  @override
  Iterable<CompletionSuggestion> suggestions(
@@ -198,7 +196,7 @@ class YamlCompletionRequest {
  final ResourceProvider resourceProvider;

  /// The Pub package service used for looking up package names/versions.
-  final PubPackageService pubPackageService;
+  final PubPackageService? pubPackageService;

  /// The absolute path of the file in which completions are being requested.
  final String filePath;
@@ -208,8 +206,8 @@ class YamlCompletionRequest {

  /// Initialize a newly created completion request.
  YamlCompletionRequest(
-      {@required this.filePath,
-      @required this.precedingText,
-      @required this.resourceProvider,
-      @required this.pubPackageService});
+      {required this.filePath,
+      required this.precedingText,
+      required this.resourceProvider,
+      required this.pubPackageService});
 }
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/services/completion/yaml/producer.dart';
 import 'package:analysis_server/src/services/completion/yaml/yaml_completion_generator.dart';
@@ -17,10 +15,12 @@ class PubPackageNameProducer extends Producer {
  @override
  Iterable<CompletionSuggestion> suggestions(
      YamlCompletionRequest request) sync* {
-    final cachedPackages = request.pubPackageService.cachedPackages;
-    var relevance = cachedPackages.length;
-    yield* cachedPackages.map((package) =>
-        packageName('${package.packageName}: ', relevance: relevance--));
+    final cachedPackages = request.pubPackageService?.cachedPackages;
+    if (cachedPackages != null) {
+      var relevance = cachedPackages.length;
+      yield* cachedPackages.map((package) =>
+          packageName('${package.packageName}: ', relevance: relevance--));
+    }
  }
 }

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/services/completion/yaml/producer.dart';
 import 'package:analysis_server/src/services/pub/pub_package_service.dart';
@@ -19,9 +17,9 @@ abstract class YamlCompletionGenerator {
  /// completion was requested.
  final ResourceProvider resourceProvider;

-  /// A service used for collecting Pub package information. May be null for
+  /// A service used for collecting Pub package information. May be `null` for
  /// generators that do not use Pub packages.
-  final PubPackageService pubPackageService;
+  final PubPackageService? pubPackageService;

  /// Initialize a newly created generator to use the [resourceProvider] to
  /// access the content of the file in which completion was requested.
@@ -86,15 +84,21 @@ abstract class YamlCompletionGenerator {
      }
    }
    final node = nodePath.isNotEmpty ? nodePath.last : null;
-    final replaceNode = node is YamlScalar && node.containsOffset(offset);
-    final replacementOffset = replaceNode ? node.span.start.offset : offset;
-    final replacementLength = replaceNode ? node.span.length : 0;
+    int replacementOffset;
+    int replacementLength;
+    if (node is YamlScalar && node.containsOffset(offset)) {
+      replacementOffset = node.span.start.offset;
+      replacementLength = node.span.length;
+    } else {
+      replacementOffset = offset;
+      replacementLength = 0;
+    }
    return YamlCompletionResults(
        suggestions, replacementOffset, replacementLength);
  }

  /// Return the result of parsing the file [content] into a YAML node.
-  YamlNode _parseYaml(String content) {
+  YamlNode? _parseYaml(String content) {
    try {
      return loadYamlNode(content, recover: true);
    } on YamlException {
@@ -108,7 +112,7 @@ abstract class YamlCompletionGenerator {
  /// and the node containing the offset is the last element in the list.
  List<YamlNode> _pathToOffset(YamlNode root, int offset) {
    var path = <YamlNode>[];
-    var node = root;
+    YamlNode? node = root;
    while (node != null) {
      path.add(node);
      node = node.childContainingOffset(offset);
@@ -118,19 +122,19 @@ abstract class YamlCompletionGenerator {

  /// Return the producer that should be used to produce completion suggestions
  /// for the last node in the node [path].
-  Producer _producerForPath(List<YamlNode> path) {
-    var producer = topLevelProducer;
+  Producer? _producerForPath(List<YamlNode> path) {
+    Producer? producer = topLevelProducer;
    for (var i = 0; i < path.length - 1; i++) {
      var node = path[i];
      if (node is YamlMap && producer is KeyValueProducer) {
        var key = node.keyAtValue(path[i + 1]);
        if (key is YamlScalar) {
-          producer = (producer as KeyValueProducer).producerForKey(key.value);
+          producer = producer.producerForKey(key.value);
        } else {
          return null;
        }
      } else if (node is YamlList && producer is ListProducer) {
-        producer = (producer as ListProducer).element;
+        producer = producer.element;
      } else {
        return producer;
      }
@@ -141,7 +145,7 @@ abstract class YamlCompletionGenerator {
  /// Return a list of the suggestions that should not be suggested because they
  /// are already in the structure.
  List<String> _siblingsOnPath(List<YamlNode> path) {
-    List<String> siblingsInList(YamlList list, YamlNode currentElement) {
+    List<String> siblingsInList(YamlList list, YamlNode? currentElement) {
      var siblings = <String>[];
      for (var element in list.nodes) {
        if (element != currentElement &&
@@ -153,7 +157,7 @@ abstract class YamlCompletionGenerator {
      return siblings;
    }

-    List<String> siblingsInMap(YamlMap map, YamlNode currentKey) {
+    List<String> siblingsInMap(YamlMap map, YamlNode? currentKey) {
      var siblings = <String>[];
      for (var key in map.nodes.keys) {
        if (key != currentKey && key is YamlScalar && key.value is String) {
@@ -41,7 +41,7 @@ class PubApi {
  };

  PubApi(this.instrumentationService, http.Client? httpClient,
-      String envPubHostedUrl)
+      String? envPubHostedUrl)
      : httpClient =
            httpClient != null ? _NoCloseHttpClient(httpClient) : http.Client(),
        _pubHostedUrl = _validPubHostedUrl(envPubHostedUrl);
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:test_reflective_loader/test_reflective_loader.dart';

 import 'protocol_dart_test.dart' as protocol_dart_test;
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/services/completion/dart/feature_computer.dart';
 import 'package:analyzer_plugin/src/utilities/completion/completion_target.dart';
 import 'package:test/test.dart';
@@ -19,10 +17,10 @@ void main() {

@reflectiveTest
 class ContextTypeTest extends FeatureComputerTest {
-  Future<void> assertContextType(String content, String expectedType) async {
+  Future<void> assertContextType(String content, [String? expectedType]) async {
    await completeIn(content);
-    var computer = FeatureComputer(
-        testAnalysisResult.typeSystem, testAnalysisResult.typeProvider);
+    var result = testAnalysisResult!;
+    var computer = FeatureComputer(result.typeSystem, result.typeProvider);
    var type = computer.computeContextType(
        completionTarget.containingNode, cursorIndex);

@@ -68,7 +66,7 @@ void f({int i = 0}) {}
 void g() {
  f(i^:);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_named_beforeLabel() async {
@@ -77,7 +75,7 @@ void f({int i = 0}) {}
 void g() {
  f(^i:);
 }
-''', null);
+''');
  }

  Future<void>
@@ -118,7 +116,7 @@ void f({int i}) {}
 void g() {
  f(j: ^);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_named_unresolved_noNamedParameters() async {
@@ -128,7 +126,7 @@ void f() {}
 void g() {
  f(j: ^);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_named_with_requiredPositional() async {
@@ -156,7 +154,7 @@ void f() {}
 void g() {
  f(^);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_noParameters_whitespace() async {
@@ -165,7 +163,7 @@ void f() {}
 void g() {
  f(  ^  );
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_noParameters_whitespace_left() async {
@@ -174,7 +172,7 @@ void f() {}
 void g() {
  f(  ^);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_noParameters_whitespace_right() async {
@@ -183,7 +181,7 @@ void f() {}
 void g() {
  f(^  );
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_positional() async {
@@ -201,7 +199,7 @@ void f([int i]) {}
 void g() {
  f(i: ^);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_positional_asNamed_beforeColon() async {
@@ -210,7 +208,7 @@ void f(String s, bool b, [int i = 0]) {}
 void g() {
  f(i^:);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_positional_asNamed_beforeLabel() async {
@@ -266,7 +264,7 @@ void f(int i, String str, bool b) {}
 void g() {
  f(i: ^);
 }
-''', null);
+''');
  }

  Future<void> test_argumentList_requiredPositional_first() async {
@@ -421,7 +419,7 @@ class C {
 void g(String s) {
  var x = ^s.length;
 }
-''', null);
+''');
  }

  Future<void> test_assignmentExpression_withType() async {
@@ -485,7 +483,7 @@ class Foo {
 class Foo {
  var x =^;
 }
-''', null);
+''');
  }

  Future<void> test_fieldDeclaration_var_impliedType_int() async {
@@ -517,7 +515,7 @@ class Foo {
 class Foo {
  var x = ^ ;
 }
-''', null);
+''');
  }

  Future<void> test_ifElement() async {
@@ -565,7 +563,7 @@ void foo() {
 void f(int e) {
  var l = ^<int>[e];
 }
-''', null);
+''');
  }

  Future<void> test_listLiteral_element() async {
@@ -589,7 +587,7 @@ void f(int e) {
 void f(int e) {
  var l = <^int>[e];
 }
-''', null);
+''');
  }

  Future<void> test_mapLiteralEntry_key() async {
@@ -633,7 +631,7 @@ void g(C c) {
 void f() {
  var m = ^<int, int>{};
 }
-''', null);
+''');
  }

  Future<void> test_setOrMapLiteral_map_element() async {
@@ -649,7 +647,7 @@ void f(bool b, int e) {
 void f() {
  var m = <int, ^int>{};
 }
-''', null);
+''');
  }

  Future<void> test_setOrMapLiteral_set_beforeTypeParameter() async {
@@ -657,7 +655,7 @@ void f() {
 void f() {
  var s = ^<int>{};
 }
-''', null);
+''');
  }

  Future<void> test_setOrMapLiteral_set_element() async {
@@ -673,7 +671,7 @@ void f(int e) {
 void f() {
  var s = <^int>{};
 }
-''', null);
+''');
  }

  Future<void> test_topLevelVariableDeclaration_int() async {
@@ -710,26 +708,26 @@ int i =  ^  ;
  Future<void> test_topLevelVariableDeclaration_var() async {
    await assertContextType('''
 var x=^;
-''', null);
+''');
  }

  Future<void> test_topLevelVariableDeclaration_var_noEqual() async {
    await assertContextType('''
 int x^;
-''', null);
+''');
  }

  Future<void> test_topLevelVariableDeclaration_var_whitespace() async {
    await assertContextType('''
 var x=  ^  ;
-''', null);
+''');
  }
 }

 abstract class FeatureComputerTest extends AbstractSingleUnitTest {
  int cursorIndex = 0;

-  CompletionTarget completionTarget;
+  late CompletionTarget completionTarget;

  @override
  bool verifyNoTestUnitErrors = false;
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/services/completion/yaml/analysis_options_generator.dart';
 import 'package:analyzer/src/task/options.dart';
 import 'package:linter/src/rules.dart';
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/services/completion/yaml/fix_data_generator.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/services/completion/yaml/pubspec_generator.dart';
 import 'package:analysis_server/src/services/pub/pub_api.dart';
 import 'package:analysis_server/src/services/pub/pub_package_service.dart';
@@ -23,9 +21,10 @@ void main() {

@reflectiveTest
 class PubspecGeneratorTest extends YamlGeneratorTest {
-  MockHttpClient httpClient;
+  late MockHttpClient httpClient;
+
+  late PubPackageService pubPackageService;

-  PubPackageService pubPackageService;
  @override
  String get fileName => 'pubspec.yaml';

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:test_reflective_loader/test_reflective_loader.dart';

 import 'analysis_options_generator_test.dart' as analysis_options_generator;
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-// @dart = 2.9
-
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/services/completion/yaml/yaml_completion_generator.dart';
 import 'package:analyzer/src/test_utilities/resource_provider_mixin.dart';
@@ -11,7 +9,7 @@ import 'package:test/test.dart';

 abstract class YamlGeneratorTest with ResourceProviderMixin {
  /// The completion results produced by [getCompletions].
-  /* late */ List<CompletionSuggestion> results;
+  late List<CompletionSuggestion> results;

  /// Return the name of the file being tested.
  String get fileName;