CPLAT-4674: Add workaround for ddc bug via props/state impl constructor

lib/src/builder/generation/impl_generation.dart

@@ -164,12 +164,17 @@ class ImplGenerator {
           ..writeln('//')
           ..writeln('// Implements constructor and backing map.')
           ..writeln('class $stateImplName$typeParamsOnClass extends $stateName$typeParamsOnSuper with $stateAccessorsMixinName$typeParamsOnSuper implements $consumableStateName$typeParamsOnSuper {')
-          ..writeln('  $stateImplName(Map backingMap) : this._state = backingMap ?? {};')
+          ..writeln('  // This initializer of `_state` to an empty map, as well as the reassignment')
+          ..writeln('  // of `_state` in the constructor body is necessary to work around an unknown ddc issue.')
+          ..writeln('  // See <https://jira.atl.workiva.net/browse/CPLAT-4673> for more details')
+          ..writeln('  $stateImplName(Map backingMap) : this._state = {} {')
+          ..writeln('     this._state = backingMap ?? {};')
+          ..writeln('  }')
           ..writeln()
           ..writeln('  /// The backing state map proxied by this class.')
           ..writeln('  @override')
           ..writeln('  Map get state => _state;')
-          ..writeln('  final Map _state;')
+          ..writeln('  Map _state;')
           ..writeln()
           ..writeln('  /// Let [UiState] internals know that this class has been generated.')
           ..writeln('  @override')
@@ -685,12 +690,17 @@ class ImplGenerator {
         ..writeln('//')
         ..writeln('// Implements constructor and backing map, and links up to generated component factory.')
         ..write(classDeclaration)
-        ..writeln('  $implName(Map backingMap) : this._props = backingMap ?? {};')
+        ..writeln('  // This initializer of `_props` to an empty map, as well as the reassignment')
+        ..writeln('  // of `_props` in the constructor body is necessary to work around an unknown ddc issue.')
+        ..writeln('  // See <https://jira.atl.workiva.net/browse/CPLAT-4673> for more details')
+        ..writeln('  $implName(Map backingMap) : this._props = {} {')
+        ..writeln('     this._props = backingMap ?? {};')
+        ..writeln('  }')
         ..writeln()
         ..writeln('  /// The backing props map proxied by this class.')
         ..writeln('  @override')
         ..writeln('  Map get props => _props;')
-        ..writeln('  final Map _props;')
+        ..writeln('  Map _props;')
         ..writeln()
         ..writeln('  /// Let [UiProps] internals know that this class has been generated.')
         ..writeln('  @override')