Offer to add parameter to constructor with no existing parameters

src/EditorFeatures/CSharpTest/GenerateFromMembers/AddConstructorParametersFromMembers/AddConstructorParametersFromMembersTests.cs

@@ -642,5 +642,46 @@ public C(int i, int hello)
 }"
             );
         }
+
+        [WorkItem(33602, "https://github.com/dotnet/roslyn/issues/33602")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddConstructorParametersFromMembers)]
+        public async Task TestConstructorWithNoParameters()
+        {
+            await TestInRegularAndScriptAsync(
+@"
+class C
+{
+    [|int i;
+    int Hello { get; set; }|]
+    public C()
+    {
+    }
+}",
+@"
+class C
+{
+    int i;
+    int Hello { get; set; }
+    public C(int i, int hello)
+    {
+        this.i = i;
+        Hello = hello;
+    }
+}"
+            );
+        }
+
+        [WorkItem(33602, "https://github.com/dotnet/roslyn/issues/33602")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddConstructorParametersFromMembers)]
+        public async Task TestDefaultConstructor()
+        {
+            await TestMissingAsync(
+@"
+class C
+{
+    [|int i;|]
+    int Hello { get; set; }
+}");
+        }
     }
 }

src/EditorFeatures/VisualBasicTest/AddConstructorParametersFromMembers/AddConstructorParametersFromMembersTests.vb

@@ -202,5 +202,40 @@ Class Program
     End Sub
 End Class")
         End Function
+
+        <WorkItem(33602, "https://github.com/dotnet/roslyn/issues/33602")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddConstructorParametersFromMembers)>
+        Public Async Function TestConstructorWithNoParameters() As Task
+            Await TestInRegularAndScriptAsync(
+"
+Class Program
+    [|Private i As Integer
+    Property Hello As Integer = 1|]
+    Public Sub New()
+    End Sub
+End Class",
+"
+Class Program
+    [|Private i As Integer
+    Property Hello As Integer = 1|]
+    Public Sub New(i As Integer, hello As Integer)
+        Me.i = i
+        Me.Hello = hello
+    End Sub
+End Class"
+)
+        End Function
+
+        <WorkItem(33602, "https://github.com/dotnet/roslyn/issues/33602")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddConstructorParametersFromMembers)>
+        Public Async Function TestDefaultConstructor() As Task
+            Await TestMissingAsync(
+"
+Class Program
+    [|Private i As Integer|]
+End Class"
+)
+
+        End Function
     End Class
 End Namespace

src/Features/Core/Portable/AddConstructorParametersFromMembers/AddConstructorParametersFromMembersCodeRefactoringProvider.State.cs

@@ -77,28 +77,31 @@ private bool TryInitialize(
             /// <summary>
             /// Try to find a constructor in <paramref name="containingType"/> whose parameters is the subset of <paramref name="parameters"/> by comparing name.
             /// If multiple constructors meet the condition, the one with more parameters will be returned.
-            /// It will not consider those constructors as potential candidates if:
-            /// 1. Constructor with empty parameter list.
-            /// 2. Constructor's parameter list contains 'ref' or 'params'
+            /// It will not consider those constructors as potential candidates if the constructor's parameter list 
+            /// contains 'ref' or 'params'
             /// </summary>
             private IMethodSymbol GetDelegatedConstructorBasedOnParameterNames(
                 INamedTypeSymbol containingType,
                 ImmutableArray<IParameterSymbol> parameters)
             {
                 var parameterNames = parameters.SelectAsArray(p => p.Name);
                 return containingType.InstanceConstructors
-                    .Where(constructor => AreParametersContainedInConstructor(constructor, parameterNames))
+                    .Where(constructor => IsApplicableConstructor(constructor, parameterNames))
                     .OrderByDescending(constructor => constructor.Parameters.Length)
                     .FirstOrDefault();
             }
 
-            private bool AreParametersContainedInConstructor(
+            private bool IsApplicableConstructor(
                 IMethodSymbol constructor,
                 ImmutableArray<string> parametersName)
             {
                 var constructorParams = constructor.Parameters;
-                return constructorParams.Length > 0
-                    && constructorParams.All(parameter => parameter.RefKind == RefKind.None)
+                if (constructorParams.Length == 0)
+                {
+                    return !constructor.IsImplicitlyDeclared;
+                }
+
+                return constructorParams.All(parameter => parameter.RefKind == RefKind.None)
                     && !constructorParams.Any(p => p.IsParams)
                     && parametersName.Except(constructorParams.Select(p => p.Name)).Any();
             }

src/Features/Core/Portable/AddConstructorParametersFromMembers/AddConstructorParametersFromMembersCodeRefactoringProvider.cs

@@ -56,9 +56,11 @@ public async Task<ImmutableArray<CodeAction>> AddConstructorParametersFromMember
 
         private IEnumerable<CodeAction> CreateCodeActions(Document document, State state)
         {
-            var lastParameter = state.ConstructorToAddTo.Parameters.Last();
-            if (!lastParameter.IsOptional)
+            var parameters = state.ConstructorToAddTo.Parameters;
+            if (parameters.Length == 0 ||
+                (parameters.Length > 0 && !parameters.Last().IsOptional))
             {
+                // return a code action to add required parameters
                 yield return new AddConstructorParametersCodeAction(this, document, state, state.MissingParameters);
             }
 
@@ -71,6 +73,7 @@ private IEnumerable<CodeAction> CreateCodeActions(Document document, State state
                 isOptional: true,
                 hasDefaultValue: true));
 
+            // return a code action to add optional parameters
             yield return new AddConstructorParametersCodeAction(this, document, state, missingParameters);
         }
     }