[cfe] Remove the behaviour for allowing no defaults on unnamed option…

…al parameters for wildcards.

Reverting https://dart-review.googlesource.com/c/sdk/+/371560.

Bug: dart-lang/language#3807
Change-Id: I3933d7d6117b90cc0a091c8e3ce1e5bcf8061ec0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/377722
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Kallen Tu <kallentu@google.com>

pkg/front_end/lib/src/source/source_library_builder.dart

@@ -1919,14 +1919,6 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       if (isOptional &&
           formal.variable!.type.isPotentiallyNonNullable &&
           !formal.hasDeclaredInitializer) {
-        // Wildcard optional parameters can't be used so we allow having no
-        // initializer.
-        if (libraryFeatures.wildcardVariables.isEnabled &&
-            formal.isWildcard &&
-            !formal.isSuperInitializingFormal &&
-            !formal.isInitializingFormal) {
-          continue;
-        }
         addProblem(
             templateOptionalNonNullableWithoutInitializerError.withArguments(
                 formal.name, formal.variable!.type),

pkg/front_end/lib/src/type_inference/inference_visitor_base.dart

@@ -2146,13 +2146,6 @@ abstract class InferenceVisitorBase implements InferenceVisitor {
       if ((isOptionalPositional || isOptionalNamed) &&
           formal.type.isPotentiallyNonNullable &&
           !formal.hasDeclaredInitializer) {
-        // Wildcard optional parameters can't be used so we allow having no
-        // initializer.
-        if (libraryFeatures.wildcardVariables.isEnabled &&
-            formal.isWildcard &&
-            !formal.isInitializingFormal) {
-          continue;
-        }
         libraryBuilder.addProblem(
             templateOptionalNonNullableWithoutInitializerError.withArguments(
                 formal.name!, formal.type),