Use default expressoins

src/Workspaces/CSharpTest/CodeGeneration/SyntaxGeneratorTests.cs

@@ -1875,7 +1875,7 @@ public class C
             var cls = cu.Members[0];
             var summary = cls.DescendantNodes(descendIntoTrivia: true).OfType<XmlElementSyntax>().First();
 
-            var summary2 = summary.WithContent(default(SyntaxList<XmlNodeSyntax>));
+            var summary2 = summary.WithContent(default);
 
             var newCu = Generator.ReplaceNode(cu, summary, summary2);
 

src/Workspaces/CSharpTest/Formatting/FormattingElasticTriviaTests.cs

@@ -38,7 +38,7 @@ class B
             var compilation = SyntaxFactory.CompilationUnit(
                 externs: SyntaxFactory.SingletonList<ExternAliasDirectiveSyntax>(
                             SyntaxFactory.ExternAliasDirective("A1")),
-                usings: default(SyntaxList<UsingDirectiveSyntax>),
+                usings: default,
                 attributeLists: SyntaxFactory.SingletonList<AttributeListSyntax>(
                                 SyntaxFactory.AttributeList(
                                     SyntaxFactory.Token(
@@ -59,15 +59,15 @@ class B
                 new MemberDeclarationSyntax[]
                 {
                     SyntaxFactory.ClassDeclaration(
-                        default(SyntaxList<AttributeListSyntax>),
+                        default,
                         SyntaxFactory.TokenList(),
                         SyntaxFactory.Identifier("My"),
                         null,
                         SyntaxFactory.BaseList(
                             SyntaxFactory.SingletonSeparatedList<BaseTypeSyntax>(
                                 SyntaxFactory.SimpleBaseType(SyntaxFactory.ParseTypeName("System.Attribute")))),
-                                default(SyntaxList<TypeParameterConstraintClauseSyntax>),
-                                default(SyntaxList<MemberDeclarationSyntax>)),
+                                default,
+                                default),
                     SyntaxFactory.ClassDeclaration("A"),
                     SyntaxFactory.ClassDeclaration(
                         attributeLists: SyntaxFactory.SingletonList<AttributeListSyntax>(
@@ -79,8 +79,8 @@ class B
                         identifier: SyntaxFactory.Identifier("B"),
                         typeParameterList: null,
                         baseList: null,
-                        constraintClauses: default(SyntaxList<TypeParameterConstraintClauseSyntax>),
-                        members: default(SyntaxList<MemberDeclarationSyntax>))
+                        constraintClauses: default,
+                        members: default)
                 }));
 
             Assert.NotNull(compilation);
@@ -148,7 +148,7 @@ public void FormatElasticTriviaBetweenPropertiesWithoutAccessors()
     string MyProperty => ""42"";
 }";
             var property = SyntaxFactory.PropertyDeclaration(
-                attributeLists: default(SyntaxList<AttributeListSyntax>),
+                attributeLists: default,
                 modifiers: SyntaxFactory.TokenList(),
                 type: SyntaxFactory.PredefinedType(
                     SyntaxFactory.Token(
@@ -165,19 +165,19 @@ public void FormatElasticTriviaBetweenPropertiesWithoutAccessors()
                 semicolonToken: SyntaxFactory.Token(SyntaxKind.SemicolonToken));
 
             var compilation = SyntaxFactory.CompilationUnit(
-                externs: default(SyntaxList<ExternAliasDirectiveSyntax>),
-                usings: default(SyntaxList<UsingDirectiveSyntax>),
-                attributeLists: default(SyntaxList<AttributeListSyntax>),
+                externs: default,
+                usings: default,
+                attributeLists: default,
                 members: SyntaxFactory.List(
                 new MemberDeclarationSyntax[]
                 {
                     SyntaxFactory.ClassDeclaration(
-                        attributeLists: default(SyntaxList<AttributeListSyntax>),
+                        attributeLists: default,
                         modifiers: SyntaxFactory.TokenList(),
                         identifier: SyntaxFactory.Identifier("PropertyTest"),
                         typeParameterList: null,
                         baseList: null,
-                        constraintClauses: default(SyntaxList<TypeParameterConstraintClauseSyntax>),
+                        constraintClauses: default,
                         members: SyntaxFactory.List(
                             new MemberDeclarationSyntax[]
                             {

src/Workspaces/CSharpTest/Formatting/FormattingTests.cs

@@ -4579,7 +4579,7 @@ public void FormatArbitaryNode()
                 SyntaxFactory.List<AttributeListSyntax>(),
                 SyntaxFactory.TokenList(SyntaxFactory.Token(SyntaxKind.PublicKeyword)),
                 SyntaxFactory.ParseTypeName("int"),
-                default(ExplicitInterfaceSpecifierSyntax),
+                default,
                 SyntaxFactory.Identifier("Prop"),
                 SyntaxFactory.AccessorList(
                     SyntaxFactory.List(