diff --git a/pkg/analyzer/lib/src/dart/analysis/feature_set_provider.dart b/pkg/analyzer/lib/src/dart/analysis/feature_set_provider.dart
index 6d38db223d0..9f3a4db3957 100644
--- a/pkg/analyzer/lib/src/dart/analysis/feature_set_provider.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/feature_set_provider.dart
@@ -12,10 +12,6 @@ import 'package:analyzer/src/util/uri.dart';
 import 'package:pub_semver/pub_semver.dart';
 
 class FeatureSetProvider {
-  /// This flag will be turned to `true` and inlined when we un-fork SDK,
-  /// so that the only SDK is the Null Safe SDK.
-  static const isNullSafetySdk = true;
-
   final Version _sdkLanguageVersion;
   final AllowedExperiments _allowedExperiments;
   final ResourceProvider _resourceProvider;
diff --git a/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart b/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart
index 9fe7223e5c7..367f7efdcf0 100644
--- a/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart
+++ b/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart
@@ -2643,7 +2643,7 @@ const c = a.codeUnitAt(b);
       invocation.methodName,
       elementMatcher(
         stringElement.getMethod('codeUnitAt'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
     );
 
@@ -8532,7 +8532,7 @@ main() {
         prefixed,
         element: elementMatcher(
           objectHashCode,
-          isLegacy: isNullSafetySdkAndLegacyLibrary,
+          isLegacy: isLegacyLibrary,
         ),
         type: 'int',
       );
@@ -8546,7 +8546,7 @@ main() {
         identifier,
         element: elementMatcher(
           objectHashCode,
-          isLegacy: isNullSafetySdkAndLegacyLibrary,
+          isLegacy: isLegacyLibrary,
         ),
         type: 'int',
       );
diff --git a/pkg/analyzer/test/src/dart/resolution/assignment_test.dart b/pkg/analyzer/test/src/dart/resolution/assignment_test.dart
index 1581d510fe9..ce3713b1e92 100644
--- a/pkg/analyzer/test/src/dart/resolution/assignment_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/assignment_test.dart
@@ -103,7 +103,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -129,7 +129,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -155,7 +155,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -228,7 +228,7 @@ class B extends A {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -254,7 +254,7 @@ class A {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -733,7 +733,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -925,7 +925,7 @@ void f() {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -963,7 +963,7 @@ void f() {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -1072,7 +1072,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -1134,7 +1134,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -1176,7 +1176,7 @@ void f(C c) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -1271,7 +1271,7 @@ class B extends A {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -1306,7 +1306,7 @@ class A {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -1623,7 +1623,7 @@ void f() {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num', // num + int = num
     );
@@ -2144,7 +2144,7 @@ class C {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -2184,7 +2184,7 @@ class C with M1, M2 {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -2281,7 +2281,7 @@ void f() {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -2349,7 +2349,7 @@ class A {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/binary_expression_test.dart b/pkg/analyzer/test/src/dart/resolution/binary_expression_test.dart
index f3f1dea00ba..5be34e43544 100644
--- a/pkg/analyzer/test/src/dart/resolution/binary_expression_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/binary_expression_test.dart
@@ -123,7 +123,7 @@ f(int a, int b) {
       findNode.binary('a != b'),
       element: elementMatcher(
         numElement.getMethod('=='),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'bool',
     );
@@ -177,7 +177,7 @@ f(int a, int b) {
       findNode.binary('a == b'),
       element: elementMatcher(
         numElement.getMethod('=='),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'bool',
     );
@@ -287,7 +287,7 @@ f(int a, double b) {
       findNode.binary('a - b'),
       element: elementMatcher(
         numElement.getMethod('-'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -304,7 +304,7 @@ f(int a, int b) {
       findNode.binary('a - b'),
       element: elementMatcher(
         numElement.getMethod('-'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -334,7 +334,7 @@ f(int a, double b) {
       findNode.binary('a % b'),
       element: elementMatcher(
         numElement.getMethod('%'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -351,7 +351,7 @@ f(int a, int b) {
       findNode.binary('a % b'),
       element: elementMatcher(
         numElement.getMethod('%'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -405,7 +405,7 @@ f(double a, dynamic b) {
       findNode.binary('a + b'),
       element: elementMatcher(
         doubleElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -489,7 +489,7 @@ f(int a, double b) {
       findNode.binary('a + b'),
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -506,7 +506,7 @@ f(int a, dynamic b) {
       findNode.binary('a + b'),
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num',
     );
@@ -523,7 +523,7 @@ f(int a, int b) {
       findNode.binary('a + b'),
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -540,7 +540,7 @@ f(int Function() a, int b) {
       findNode.binary('a() + b'),
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -577,7 +577,7 @@ f(int a, num b) {
       findNode.binary('a + b'),
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num',
     );
@@ -741,7 +741,7 @@ f<T extends num>(T a) {
       findNode.binary('a + 0'),
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num',
     );
@@ -758,7 +758,7 @@ f(int a, int b) {
       findNode.binary('a / b'),
       element: elementMatcher(
         numElement.getMethod('/'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -788,7 +788,7 @@ f(int a, double b) {
       findNode.binary('a * b'),
       element: elementMatcher(
         numElement.getMethod('*'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -805,7 +805,7 @@ f(int a, int b) {
       findNode.binary('a * b'),
       element: elementMatcher(
         numElement.getMethod('*'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/extension_override_test.dart b/pkg/analyzer/test/src/dart/resolution/extension_override_test.dart
index 946f22306d5..3a737e2b7a4 100644
--- a/pkg/analyzer/test/src/dart/resolution/extension_override_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/extension_override_test.dart
@@ -630,7 +630,7 @@ void f(A a) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -664,7 +664,7 @@ void f(A a) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -699,7 +699,7 @@ void f(p.A a) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -740,7 +740,7 @@ void f(p.A a) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/index_expression_test.dart b/pkg/analyzer/test/src/dart/resolution/index_expression_test.dart
index e10926e4ffb..20e87bf969d 100644
--- a/pkg/analyzer/test/src/dart/resolution/index_expression_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/index_expression_test.dart
@@ -187,7 +187,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numPlusElement,
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: typeToStringWithNullability ? 'double' : 'num',
     );
@@ -248,7 +248,7 @@ void f(A<double> a) {
       writeType: 'double',
       operatorElement: elementMatcher(
         doublePlusElement,
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/method_invocation_test.dart b/pkg/analyzer/test/src/dart/resolution/method_invocation_test.dart
index a76e41a9ddb..3b573d9048b 100644
--- a/pkg/analyzer/test/src/dart/resolution/method_invocation_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/method_invocation_test.dart
@@ -77,7 +77,7 @@ f(double a, double b, double c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: typeToStringWithNullability ? 'double' : 'num');
   }
@@ -92,7 +92,7 @@ f(double a, double b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -107,7 +107,7 @@ f(double a, int b, double c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -122,7 +122,7 @@ f(double a, int b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -181,7 +181,7 @@ f(int a, double b, double c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -196,7 +196,7 @@ f(int a, double b, dynamic c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -211,7 +211,7 @@ f(int a, double b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -226,7 +226,7 @@ f(int a, dynamic b, double c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -241,7 +241,7 @@ f(int a, dynamic b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -256,7 +256,7 @@ f(int a, int b, double c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -271,7 +271,7 @@ f(int a, int b, dynamic c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -286,7 +286,7 @@ f(int a, int b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: typeToStringWithNullability ? 'int' : 'num');
   }
@@ -305,7 +305,7 @@ f(int a, int b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: typeToStringWithNullability ? 'int' : 'num');
   }
@@ -337,7 +337,7 @@ f(int a, int b, Never c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -356,7 +356,7 @@ f(int a, Never b, int c) {
     assertMethodInvocation(
         findNode.methodInvocation('clamp'),
         elementMatcher(numElement.getMethod('clamp'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num, num)',
         expectedType: 'num');
   }
@@ -2122,7 +2122,7 @@ void f(a) {
       findNode.methodInvocation('toString()'),
       element: elementMatcher(
         objectElement.getMethod('toString'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       typeArgumentTypes: [],
       invokeType: 'String Function()',
@@ -2223,7 +2223,7 @@ f(int a, double b) {
     assertMethodInvocation(
         findNode.methodInvocation('remainder'),
         elementMatcher(numElement.getMethod('remainder'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num)',
         expectedType: typeToStringWithNullability ? 'double' : 'num');
   }
@@ -2238,7 +2238,7 @@ f(int a, int b) {
     assertMethodInvocation(
         findNode.methodInvocation('remainder'),
         elementMatcher(numElement.getMethod('remainder'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num)',
         expectedType: typeToStringWithNullability ? 'int' : 'num');
   }
@@ -2253,7 +2253,7 @@ f(int Function() a, int b) {
     assertMethodInvocation(
         findNode.methodInvocation('remainder'),
         elementMatcher(numElement.getMethod('remainder'),
-            isLegacy: isNullSafetySdkAndLegacyLibrary),
+            isLegacy: isLegacyLibrary),
         'num Function(num)',
         expectedType: typeToStringWithNullability ? 'int' : 'num');
   }
diff --git a/pkg/analyzer/test/src/dart/resolution/postfix_expression_test.dart b/pkg/analyzer/test/src/dart/resolution/postfix_expression_test.dart
index 2c5f4431487..3cfabd6eec6 100644
--- a/pkg/analyzer/test/src/dart/resolution/postfix_expression_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/postfix_expression_test.dart
@@ -319,7 +319,7 @@ void f(int x) {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('-'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -345,7 +345,7 @@ void f(A a) {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -373,7 +373,7 @@ class B extends A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -399,7 +399,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -489,7 +489,7 @@ void f(A a) {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -518,7 +518,7 @@ void f() {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -546,7 +546,7 @@ void f() {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -577,7 +577,7 @@ class B extends A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -603,7 +603,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -624,7 +624,7 @@ void f(double x) {
       writeType: 'double',
       element: elementMatcher(
         doubleElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -645,7 +645,7 @@ void f(int x) {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -666,7 +666,7 @@ void f(num x) {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num',
     );
@@ -695,7 +695,7 @@ class B extends A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -725,7 +725,7 @@ void f() {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -757,7 +757,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/prefix_expression_test.dart b/pkg/analyzer/test/src/dart/resolution/prefix_expression_test.dart
index 1fa6d56f621..34082374d5c 100644
--- a/pkg/analyzer/test/src/dart/resolution/prefix_expression_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/prefix_expression_test.dart
@@ -234,7 +234,7 @@ void f(A a) {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -262,7 +262,7 @@ class B extends A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -288,7 +288,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -309,7 +309,7 @@ void f(int x) {
       writeType: null,
       element: elementMatcher(
         intElement.getMethod('unary-'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -382,7 +382,7 @@ void f(A a) {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -411,7 +411,7 @@ void f() {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -439,7 +439,7 @@ void f() {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -470,7 +470,7 @@ class B extends A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -496,7 +496,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -517,7 +517,7 @@ void f(double x) {
       writeType: 'double',
       element: elementMatcher(
         doubleElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'double',
     );
@@ -538,7 +538,7 @@ void f(int x) {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -559,7 +559,7 @@ void f(num x) {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num',
     );
@@ -585,7 +585,7 @@ void f<T extends num>(T x) {
       writeType: 'T',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'num',
     );
@@ -614,7 +614,7 @@ class B extends A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -644,7 +644,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -674,7 +674,7 @@ void f() {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -706,7 +706,7 @@ class A {
       writeType: 'num',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -735,7 +735,7 @@ class A {
       writeType: 'int',
       element: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -756,7 +756,7 @@ void f(int x) {
       writeType: null,
       element: elementMatcher(
         intElement.getMethod('~'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/prefixed_identifier_test.dart b/pkg/analyzer/test/src/dart/resolution/prefixed_identifier_test.dart
index e1fcbccb624..dc81aabbd6b 100644
--- a/pkg/analyzer/test/src/dart/resolution/prefixed_identifier_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/prefixed_identifier_test.dart
@@ -220,7 +220,7 @@ void f(A a) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/property_access_test.dart b/pkg/analyzer/test/src/dart/resolution/property_access_test.dart
index e3ef89b03fd..d57c5ea8223 100644
--- a/pkg/analyzer/test/src/dart/resolution/property_access_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/property_access_test.dart
@@ -223,7 +223,7 @@ void f(A a) {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -335,7 +335,7 @@ void f() {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -472,7 +472,7 @@ void f() {
       writeType: 'num',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -578,7 +578,7 @@ class B extends A {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/dart/resolution/resolution.dart b/pkg/analyzer/test/src/dart/resolution/resolution.dart
index 63a93dbb6c3..9cdf492b55a 100644
--- a/pkg/analyzer/test/src/dart/resolution/resolution.dart
+++ b/pkg/analyzer/test/src/dart/resolution/resolution.dart
@@ -9,7 +9,6 @@ import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/dart/element/type_provider.dart';
 import 'package:analyzer/error/error.dart';
-import 'package:analyzer/src/dart/analysis/feature_set_provider.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer/src/dart/element/element.dart';
@@ -57,11 +56,8 @@ mixin ResolutionTest implements ResourceProviderMixin {
 
   InterfaceType get intType => typeProvider.intType;
 
-  bool get isNullSafetySdkAndLegacyLibrary {
-    if (FeatureSetProvider.isNullSafetySdk) {
-      return !result.libraryElement.isNonNullableByDefault;
-    }
-    return false;
+  bool get isLegacyLibrary {
+    return !result.libraryElement.isNonNullableByDefault;
   }
 
   ClassElement get listElement => typeProvider.listElement;
diff --git a/pkg/analyzer/test/src/diagnostics/receiver_of_type_never_test.dart b/pkg/analyzer/test/src/diagnostics/receiver_of_type_never_test.dart
index c64b59274cd..a120a6ffa85 100644
--- a/pkg/analyzer/test/src/diagnostics/receiver_of_type_never_test.dart
+++ b/pkg/analyzer/test/src/diagnostics/receiver_of_type_never_test.dart
@@ -571,7 +571,7 @@ void f() {
       findNode.binary('=='),
       element: elementMatcher(
         objectElement.getMethod('=='),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'bool',
     );
@@ -621,7 +621,7 @@ void f() {
       findNode.simple('toString'),
       element: elementMatcher(
         objectElement.getMethod('toString'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'String Function()',
     );
@@ -638,7 +638,7 @@ void f() {
       findNode.simple('hashCode'),
       element: elementMatcher(
         objectElement.getGetter('hashCode'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
diff --git a/pkg/analyzer/test/src/diagnostics/return_of_invalid_type_test.dart b/pkg/analyzer/test/src/diagnostics/return_of_invalid_type_test.dart
index ab0bbca832d..cfe890278ca 100644
--- a/pkg/analyzer/test/src/diagnostics/return_of_invalid_type_test.dart
+++ b/pkg/analyzer/test/src/diagnostics/return_of_invalid_type_test.dart
@@ -340,7 +340,7 @@ class A {
 
   @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/38162')
   test_method_async_block_callable_class() async {
-    if (isNullSafetySdkAndLegacyLibrary) {
+    if (isLegacyLibrary) {
       throw 'Make it fail for Null Safety as well, for now.';
     }
 
diff --git a/pkg/analyzer/test/src/diagnostics/use_of_nullable_value_test.dart b/pkg/analyzer/test/src/diagnostics/use_of_nullable_value_test.dart
index 64accd64fa0..8eec4b23230 100644
--- a/pkg/analyzer/test/src/diagnostics/use_of_nullable_value_test.dart
+++ b/pkg/analyzer/test/src/diagnostics/use_of_nullable_value_test.dart
@@ -505,7 +505,7 @@ m(B b) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -518,7 +518,7 @@ m(B b) {
       writeType: 'int?',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -561,7 +561,7 @@ m(B b) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int?',
     );
@@ -574,7 +574,7 @@ m(B b) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -608,7 +608,7 @@ m(int x, int? y) {
       writeType: 'int',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );
@@ -621,7 +621,7 @@ m(int x, int? y) {
       writeType: 'int?',
       operatorElement: elementMatcher(
         numElement.getMethod('+'),
-        isLegacy: isNullSafetySdkAndLegacyLibrary,
+        isLegacy: isLegacyLibrary,
       ),
       type: 'int',
     );