diff --git a/pkg/front_end/lib/src/codes/cfe_codes_generated.dart b/pkg/front_end/lib/src/codes/cfe_codes_generated.dart
index ef100fb70bd..92da17deb98 100644
--- a/pkg/front_end/lib/src/codes/cfe_codes_generated.dart
+++ b/pkg/front_end/lib/src/codes/cfe_codes_generated.dart
@@ -4241,96 +4241,6 @@ Message _withArgumentsSpreadMapEntryElementKeyTypeMismatch(
   );
 }
 
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<Message Function(DartType _type, DartType _type2)>
-    templateSpreadMapEntryElementKeyTypeMismatchNullability =
-    const Template<Message Function(DartType _type, DartType _type2)>(
-  "SpreadMapEntryElementKeyTypeMismatchNullability",
-  problemMessageTemplate:
-      r"""Can't assign spread entry keys of type '#type' to map entry keys of type '#type2' because '#type' is nullable and '#type2' isn't.""",
-  withArguments: _withArgumentsSpreadMapEntryElementKeyTypeMismatchNullability,
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Message Function(DartType _type, DartType _type2)>
-    codeSpreadMapEntryElementKeyTypeMismatchNullability =
-    const Code<Message Function(DartType _type, DartType _type2)>(
-  "SpreadMapEntryElementKeyTypeMismatchNullability",
-  analyzerCodes: <String>["MAP_KEY_TYPE_NOT_ASSIGNABLE"],
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArgumentsSpreadMapEntryElementKeyTypeMismatchNullability(
-    DartType _type, DartType _type2) {
-  TypeLabeler labeler = new TypeLabeler();
-  List<Object> typeParts = labeler.labelType(_type);
-  List<Object> type2Parts = labeler.labelType(_type2);
-  String type = typeParts.join();
-  String type2 = type2Parts.join();
-  return new Message(
-    codeSpreadMapEntryElementKeyTypeMismatchNullability,
-    problemMessage:
-        """Can't assign spread entry keys of type '${type}' to map entry keys of type '${type2}' because '${type}' is nullable and '${type2}' isn't.""" +
-            labeler.originMessages,
-    arguments: {
-      'type': _type,
-      'type2': _type2,
-    },
-  );
-}
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>
-    templateSpreadMapEntryElementKeyTypeMismatchPartNullability =
-    const Template<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>(
-  "SpreadMapEntryElementKeyTypeMismatchPartNullability",
-  problemMessageTemplate:
-      r"""Can't assign spread entry keys of type '#type' to map entry keys of type '#type2' because '#type3' is nullable and '#type4' isn't.""",
-  withArguments:
-      _withArgumentsSpreadMapEntryElementKeyTypeMismatchPartNullability,
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>
-    codeSpreadMapEntryElementKeyTypeMismatchPartNullability = const Code<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>(
-  "SpreadMapEntryElementKeyTypeMismatchPartNullability",
-  analyzerCodes: <String>["MAP_KEY_TYPE_NOT_ASSIGNABLE"],
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArgumentsSpreadMapEntryElementKeyTypeMismatchPartNullability(
-    DartType _type, DartType _type2, DartType _type3, DartType _type4) {
-  TypeLabeler labeler = new TypeLabeler();
-  List<Object> typeParts = labeler.labelType(_type);
-  List<Object> type2Parts = labeler.labelType(_type2);
-  List<Object> type3Parts = labeler.labelType(_type3);
-  List<Object> type4Parts = labeler.labelType(_type4);
-  String type = typeParts.join();
-  String type2 = type2Parts.join();
-  String type3 = type3Parts.join();
-  String type4 = type4Parts.join();
-  return new Message(
-    codeSpreadMapEntryElementKeyTypeMismatchPartNullability,
-    problemMessage:
-        """Can't assign spread entry keys of type '${type}' to map entry keys of type '${type2}' because '${type3}' is nullable and '${type4}' isn't.""" +
-            labeler.originMessages,
-    arguments: {
-      'type': _type,
-      'type2': _type2,
-      'type3': _type3,
-      'type4': _type4,
-    },
-  );
-}
-
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(DartType _type, DartType _type2)>
     templateSpreadMapEntryElementValueTypeMismatch =
@@ -4369,97 +4279,6 @@ Message _withArgumentsSpreadMapEntryElementValueTypeMismatch(
   );
 }
 
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<Message Function(DartType _type, DartType _type2)>
-    templateSpreadMapEntryElementValueTypeMismatchNullability =
-    const Template<Message Function(DartType _type, DartType _type2)>(
-  "SpreadMapEntryElementValueTypeMismatchNullability",
-  problemMessageTemplate:
-      r"""Can't assign spread entry values of type '#type' to map entry values of type '#type2' because '#type' is nullable and '#type2' isn't.""",
-  withArguments:
-      _withArgumentsSpreadMapEntryElementValueTypeMismatchNullability,
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Message Function(DartType _type, DartType _type2)>
-    codeSpreadMapEntryElementValueTypeMismatchNullability =
-    const Code<Message Function(DartType _type, DartType _type2)>(
-  "SpreadMapEntryElementValueTypeMismatchNullability",
-  analyzerCodes: <String>["MAP_VALUE_TYPE_NOT_ASSIGNABLE"],
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArgumentsSpreadMapEntryElementValueTypeMismatchNullability(
-    DartType _type, DartType _type2) {
-  TypeLabeler labeler = new TypeLabeler();
-  List<Object> typeParts = labeler.labelType(_type);
-  List<Object> type2Parts = labeler.labelType(_type2);
-  String type = typeParts.join();
-  String type2 = type2Parts.join();
-  return new Message(
-    codeSpreadMapEntryElementValueTypeMismatchNullability,
-    problemMessage:
-        """Can't assign spread entry values of type '${type}' to map entry values of type '${type2}' because '${type}' is nullable and '${type2}' isn't.""" +
-            labeler.originMessages,
-    arguments: {
-      'type': _type,
-      'type2': _type2,
-    },
-  );
-}
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>
-    templateSpreadMapEntryElementValueTypeMismatchPartNullability =
-    const Template<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>(
-  "SpreadMapEntryElementValueTypeMismatchPartNullability",
-  problemMessageTemplate:
-      r"""Can't assign spread entry values of type '#type' to map entry values of type '#type2' because '#type3' is nullable and '#type4' isn't.""",
-  withArguments:
-      _withArgumentsSpreadMapEntryElementValueTypeMismatchPartNullability,
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>
-    codeSpreadMapEntryElementValueTypeMismatchPartNullability = const Code<
-        Message Function(
-            DartType _type, DartType _type2, DartType _type3, DartType _type4)>(
-  "SpreadMapEntryElementValueTypeMismatchPartNullability",
-  analyzerCodes: <String>["MAP_VALUE_TYPE_NOT_ASSIGNABLE"],
-);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArgumentsSpreadMapEntryElementValueTypeMismatchPartNullability(
-    DartType _type, DartType _type2, DartType _type3, DartType _type4) {
-  TypeLabeler labeler = new TypeLabeler();
-  List<Object> typeParts = labeler.labelType(_type);
-  List<Object> type2Parts = labeler.labelType(_type2);
-  List<Object> type3Parts = labeler.labelType(_type3);
-  List<Object> type4Parts = labeler.labelType(_type4);
-  String type = typeParts.join();
-  String type2 = type2Parts.join();
-  String type3 = type3Parts.join();
-  String type4 = type4Parts.join();
-  return new Message(
-    codeSpreadMapEntryElementValueTypeMismatchPartNullability,
-    problemMessage:
-        """Can't assign spread entry values of type '${type}' to map entry values of type '${type2}' because '${type3}' is nullable and '${type4}' isn't.""" +
-            labeler.originMessages,
-    arguments: {
-      'type': _type,
-      'type2': _type2,
-      'type3': _type3,
-      'type4': _type4,
-    },
-  );
-}
-
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(DartType _type)>
     templateSpreadMapEntryTypeMismatch =
diff --git a/pkg/front_end/lib/src/type_inference/inference_visitor.dart b/pkg/front_end/lib/src/type_inference/inference_visitor.dart
index 9f88e28ae23..b97a637ed20 100644
--- a/pkg/front_end/lib/src/type_inference/inference_visitor.dart
+++ b/pkg/front_end/lib/src/type_inference/inference_visitor.dart
@@ -4464,68 +4464,18 @@ class InferenceVisitorImpl extends InferenceVisitorBase
       Expression? keyError;
       Expression? valueError;
       if (!isAssignable(inferredKeyType, actualKeyType)) {
-        IsSubtypeOf subtypeCheckResult =
-            typeSchemaEnvironment.performNullabilityAwareSubtypeCheck(
-                actualKeyType, inferredKeyType);
-        if (subtypeCheckResult.isSubtypeWhenIgnoringNullabilities()) {
-          if (actualKeyType == subtypeCheckResult.subtype &&
-              inferredKeyType == subtypeCheckResult.supertype) {
-            keyError = helper.buildProblem(
-                templateSpreadMapEntryElementKeyTypeMismatchNullability
-                    .withArguments(actualKeyType, inferredKeyType),
-                entry.expression.fileOffset,
-                1);
-          } else {
-            keyError = helper.buildProblem(
-                // ignore: lines_longer_than_80_chars
-                templateSpreadMapEntryElementKeyTypeMismatchPartNullability
-                    .withArguments(
-                        actualKeyType,
-                        inferredKeyType,
-                        subtypeCheckResult.subtype!,
-                        subtypeCheckResult.supertype!),
-                entry.expression.fileOffset,
-                1);
-          }
-        } else {
-          keyError = helper.buildProblem(
-              templateSpreadMapEntryElementKeyTypeMismatch.withArguments(
-                  actualKeyType, inferredKeyType),
-              entry.expression.fileOffset,
-              1);
-        }
+        keyError = helper.buildProblem(
+            templateSpreadMapEntryElementKeyTypeMismatch.withArguments(
+                actualKeyType, inferredKeyType),
+            entry.expression.fileOffset,
+            1);
       }
       if (!isAssignable(inferredValueType, actualValueType)) {
-        IsSubtypeOf subtypeCheckResult =
-            typeSchemaEnvironment.performNullabilityAwareSubtypeCheck(
-                actualValueType, inferredValueType);
-        if (subtypeCheckResult.isSubtypeWhenIgnoringNullabilities()) {
-          if (actualValueType == subtypeCheckResult.subtype &&
-              inferredValueType == subtypeCheckResult.supertype) {
-            valueError = helper.buildProblem(
-                templateSpreadMapEntryElementValueTypeMismatchNullability
-                    .withArguments(actualValueType, inferredValueType),
-                entry.expression.fileOffset,
-                1);
-          } else {
-            valueError = helper.buildProblem(
-                // ignore: lines_longer_than_80_chars
-                templateSpreadMapEntryElementValueTypeMismatchPartNullability
-                    .withArguments(
-                        actualValueType,
-                        inferredValueType,
-                        subtypeCheckResult.subtype!,
-                        subtypeCheckResult.supertype!),
-                entry.expression.fileOffset,
-                1);
-          }
-        } else {
-          valueError = helper.buildProblem(
-              templateSpreadMapEntryElementValueTypeMismatch.withArguments(
-                  actualValueType, inferredValueType),
-              entry.expression.fileOffset,
-              1);
-        }
+        valueError = helper.buildProblem(
+            templateSpreadMapEntryElementValueTypeMismatch.withArguments(
+                actualValueType, inferredValueType),
+            entry.expression.fileOffset,
+            1);
       }
       if (spreadType.isPotentiallyNullable &&
           spreadType is! DynamicType &&
diff --git a/pkg/front_end/messages.yaml b/pkg/front_end/messages.yaml
index b93a9b9a8c1..38ecb64e229 100644
--- a/pkg/front_end/messages.yaml
+++ b/pkg/front_end/messages.yaml
@@ -5181,24 +5181,6 @@ SpreadMapEntryElementKeyTypeMismatch:
       Map<int, int> b = <int, int>{...a};
     }
 
-SpreadMapEntryElementKeyTypeMismatchNullability:
-  problemMessage: "Can't assign spread entry keys of type '#type' to map entry keys of type '#type2' because '#type' is nullable and '#type2' isn't."
-  analyzerCode: MAP_KEY_TYPE_NOT_ASSIGNABLE
-  script: >
-    main() {
-      Map<String?, int> a = <String?, int>{"foo": 42, null: 87};
-      Map<String, int> b = <String, int>{...a};
-    }
-
-SpreadMapEntryElementKeyTypeMismatchPartNullability:
-  problemMessage: "Can't assign spread entry keys of type '#type' to map entry keys of type '#type2' because '#type3' is nullable and '#type4' isn't."
-  analyzerCode: MAP_KEY_TYPE_NOT_ASSIGNABLE
-  script: >
-    main() {
-      Map<List<String?>, int> a = <List<String?>, int>{["foo"]: 42, [null]: 87};
-      Map<List<String>, int> b = <List<String>, int>{...a};
-    }
-
 SpreadMapEntryElementValueTypeMismatch:
   problemMessage: "Can't assign spread entry values of type '#type' to map entry values of type '#type2'."
   analyzerCode: MAP_VALUE_TYPE_NOT_ASSIGNABLE
@@ -5208,24 +5190,6 @@ SpreadMapEntryElementValueTypeMismatch:
       Map<String, String> b = <String, String>{...a};
     }
 
-SpreadMapEntryElementValueTypeMismatchNullability:
-  problemMessage: "Can't assign spread entry values of type '#type' to map entry values of type '#type2' because '#type' is nullable and '#type2' isn't."
-  analyzerCode: MAP_VALUE_TYPE_NOT_ASSIGNABLE
-  script: >
-    main() {
-      Map<String, int?> a = <String, int?>{"foo": 42, "bar": null};
-      Map<String, int> b = <String, int>{...a};
-    }
-
-SpreadMapEntryElementValueTypeMismatchPartNullability:
-  problemMessage: "Can't assign spread entry values of type '#type' to map entry values of type '#type2' because '#type3' is nullable and '#type4' isn't."
-  analyzerCode: MAP_VALUE_TYPE_NOT_ASSIGNABLE
-  script: >
-    main() {
-      Map<String, List<int?>> a = <String, List<int?>>{"foo": [42], "bar": [null]};
-      Map<String, List<int>> b = <String, List<int>>{...a};
-    }
-
 CantDisambiguateNotEnoughInformation:
   problemMessage: "Not enough type information to disambiguate between literal set and literal map."
   correctionMessage: "Try providing type arguments for the literal explicitly to disambiguate it."
diff --git a/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.expect b/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.expect
index f418868a1d7..746aa61c039 100644
--- a/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.expect
@@ -24,13 +24,13 @@ library;
 //   <A>[...l2]; // Error.
 //          ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <A, A>{...m}; // Error.
 //             ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <A, A>{...m}; // Error.
@@ -103,14 +103,14 @@ library;
 //   <List<A>>[...l]; // Error.
 //                ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>'.
 //  - 'List' is from 'dart:core'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <List<A>, List<A>>{...m}; // Error.
 //                         ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>'.
 //  - 'List' is from 'dart:core'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
@@ -221,11 +221,11 @@ static method foo(self::B? x, core::List<self::B?> l, core::Map<self::B?, self::
   <self::A>[invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:32:10: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
   <A>[...l2]; // Error.
          ^"];
-  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
+  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <A, A>{...m}; // Error.
-            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
+            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <A, A>{...m}; // Error.
@@ -303,12 +303,12 @@ static method bar(core::List<self::B?> x, core::List<core::List<self::B?>> l, co
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <List<A>>[...l]; // Error.
                ^"];
-  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>'.
  - 'List' is from 'dart:core'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <List<A>, List<A>>{...m}; // Error.
-                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>'.
  - 'List' is from 'dart:core'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
diff --git a/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.modular.expect b/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.modular.expect
index f418868a1d7..746aa61c039 100644
--- a/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.modular.expect
+++ b/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.modular.expect
@@ -24,13 +24,13 @@ library;
 //   <A>[...l2]; // Error.
 //          ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <A, A>{...m}; // Error.
 //             ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <A, A>{...m}; // Error.
@@ -103,14 +103,14 @@ library;
 //   <List<A>>[...l]; // Error.
 //                ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>'.
 //  - 'List' is from 'dart:core'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <List<A>, List<A>>{...m}; // Error.
 //                         ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>'.
 //  - 'List' is from 'dart:core'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
@@ -221,11 +221,11 @@ static method foo(self::B? x, core::List<self::B?> l, core::Map<self::B?, self::
   <self::A>[invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:32:10: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
   <A>[...l2]; // Error.
          ^"];
-  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
+  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <A, A>{...m}; // Error.
-            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
+            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <A, A>{...m}; // Error.
@@ -303,12 +303,12 @@ static method bar(core::List<self::B?> x, core::List<core::List<self::B?>> l, co
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <List<A>>[...l]; // Error.
                ^"];
-  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>'.
  - 'List' is from 'dart:core'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <List<A>, List<A>>{...m}; // Error.
-                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>'.
  - 'List' is from 'dart:core'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
diff --git a/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.transformed.expect
index 9375d63d789..1550bbd067a 100644
--- a/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/assignability_error_messages.dart.strong.transformed.expect
@@ -24,13 +24,13 @@ library;
 //   <A>[...l2]; // Error.
 //          ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <A, A>{...m}; // Error.
 //             ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <A, A>{...m}; // Error.
@@ -103,14 +103,14 @@ library;
 //   <List<A>>[...l]; // Error.
 //                ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>'.
 //  - 'List' is from 'dart:core'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //   <List<A>, List<A>>{...m}; // Error.
 //                         ^
 //
-// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>'.
 //  - 'List' is from 'dart:core'.
 //  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 //  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
@@ -221,11 +221,11 @@ static method foo(self::B? x, core::List<self::B?> l, core::Map<self::B?, self::
   core::_GrowableList::_literal1<self::A>(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:32:10: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
   <A>[...l2]; // Error.
          ^");
-  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
+  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <A, A>{...m}; // Error.
-            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
+            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <A, A>{...m}; // Error.
@@ -314,12 +314,12 @@ static method bar(core::List<self::B?> x, core::List<core::List<self::B?>> l, co
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <List<A>>[...l]; // Error.
                ^");
-  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>'.
  - 'List' is from 'dart:core'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
   <List<A>, List<A>>{...m}; // Error.
-                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
+                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>'.
  - 'List' is from 'dart:core'.
  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.