[cfe] Remove nullaiblity requirement from shape sufficiency checks

Closes #60076

Change-Id: I294056317cb4d6102d53efc95cadd4992f017339
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/408520
Reviewed-by: Martin Kustermann <[email protected]>
Commit-Queue: Chloe Stefantsova <[email protected]>

Author: chloestefantsova

pkg/front_end/test/type_inference/type_schema_environment_nnbd_test.dart

@@ -1881,7 +1881,7 @@ class TypeSchemaEnvironmentTest extends TypeSchemaEnvironmentTestBase {
         expressionStaticType: "A<int>?",
         checkTargetType: "C<dynamic>",
         typeParameters: "",
-        sufficiency: TypeShapeCheckSufficiency.insufficient);
+        sufficiency: TypeShapeCheckSufficiency.interfaceShape);
     checkTypeShapeCheckSufficiency(
         expressionStaticType: "B",
         checkTargetType: "C<int>?",
@@ -1891,7 +1891,7 @@ class TypeSchemaEnvironmentTest extends TypeSchemaEnvironmentTestBase {
         expressionStaticType: "B?",
         checkTargetType: "C<Object?>",
         typeParameters: "",
-        sufficiency: TypeShapeCheckSufficiency.insufficient);
+        sufficiency: TypeShapeCheckSufficiency.interfaceShape);
     checkTypeShapeCheckSufficiency(
         expressionStaticType: "B",
         checkTargetType: "C<Object?>?",
@@ -1927,7 +1927,7 @@ class TypeSchemaEnvironmentTest extends TypeSchemaEnvironmentTestBase {
         expressionStaticType: "D<int>?",
         checkTargetType: "E<dynamic>",
         typeParameters: "",
-        sufficiency: TypeShapeCheckSufficiency.insufficient);
+        sufficiency: TypeShapeCheckSufficiency.interfaceShape);
     checkTypeShapeCheckSufficiency(
         expressionStaticType: "D<num>",
         checkTargetType: "E<int>?",
@@ -1968,7 +1968,7 @@ class TypeSchemaEnvironmentTest extends TypeSchemaEnvironmentTestBase {
         expressionStaticType: "F<int>?",
         checkTargetType: "G<dynamic, Object?>",
         typeParameters: "",
-        sufficiency: TypeShapeCheckSufficiency.insufficient);
+        sufficiency: TypeShapeCheckSufficiency.interfaceShape);
     checkTypeShapeCheckSufficiency(
         expressionStaticType: "F<int>",
         checkTargetType: "G<int, Object?>?",

pkg/kernel/lib/type_environment.dart

@@ -293,11 +293,7 @@ abstract class TypeEnvironment extends Types {
       {required DartType expressionStaticType,
       required DartType checkTargetType,
       required SubtypeCheckMode subtypeCheckMode}) {
-    if (!IsSubtypeOf.basedSolelyOnNullabilities(
-            expressionStaticType, checkTargetType)
-        .inMode(subtypeCheckMode)) {
-      return TypeShapeCheckSufficiency.insufficient;
-    } else if (checkTargetType is InterfaceType &&
+    if (checkTargetType is InterfaceType &&
         expressionStaticType is InterfaceType) {
       // Analyze if an interface shape check is sufficient.