Merge pull request github#15050 from michaelnebel/csharp/defaultparamobject

C#: Default parameters for object using attributes.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expression.cs

@@ -202,16 +202,6 @@ private static bool ContainsPattern(SyntaxNode node) =>
                 return Default.CreateGenerated(cx, parent, childIndex, location, parameter.Type.IsReferenceType ? ValueAsString(null) : null);
             }
 
-            if (parameter.Type.SpecialType is SpecialType.System_Object)
-            {
-                // this can happen in VB.NET
-                cx.ExtractionError($"Extracting default argument value 'object {parameter.Name} = default' instead of 'object {parameter.Name} = {defaultValue}'. The latter is not supported in C#.",
-                    null, null, severity: Semmle.Util.Logging.Severity.Warning);
-
-                // we're generating a default expression:
-                return Default.CreateGenerated(cx, parent, childIndex, location, ValueAsString(null));
-            }
-
             if (type.SpecialType is SpecialType.None)
             {
                 return ImplicitCast.CreateGeneratedConversion(cx, parent, childIndex, type, defaultValue, location);
@@ -222,7 +212,9 @@ private static bool ContainsPattern(SyntaxNode node) =>
                 return DateTimeObjectCreation.CreateGenerated(cx, parent, childIndex, type, defaultValue, location);
             }
 
-            if (type.SpecialType is SpecialType.System_IntPtr || type.SpecialType is SpecialType.System_UIntPtr)
+            if (type.SpecialType is SpecialType.System_Object ||
+                type.SpecialType is SpecialType.System_IntPtr ||
+                type.SpecialType is SpecialType.System_UIntPtr)
             {
                 return ImplicitCast.CreateGenerated(cx, parent, childIndex, type, defaultValue, location);
             }

csharp/ql/test/library-tests/parameters/Parameters.cs

@@ -29,6 +29,7 @@ public class Parameters
     public void M21([Optional, DefaultParameterValue("mystring")] MyStruct arg10) => throw null;
     public void M22(nuint arg11 = 0) => throw null;
     public void M23(nint arg12 = 0) => throw null;
+    public void M24([Optional, DefaultParameterValue(7)] object arg13) => throw null;
 
     public struct MyStruct
     {

csharp/ql/test/library-tests/parameters/Parameters.cs_

@@ -29,6 +29,7 @@ public class ParametersDll
     public void M21([Optional, DefaultParameterValue("mystring")] MyStruct arg10) => throw null;
     public void M22(nuint arg11 = 0) => throw null;
     public void M23(nint arg12 = 0) => throw null;
+    public void M24([Optional, DefaultParameterValue(7)] object arg13) => throw null;
 
     public struct MyStruct
     {

csharp/ql/test/library-tests/parameters/Parameters.dll

@@ -5,8 +5,8 @@ noDefaultValue
 | Parameters.cs:8:17:8:18 | M2 | Parameters.cs:8:24:8:24 | a | 0 |
 | Parameters.cs:12:17:12:18 | M6 | Parameters.cs:12:29:12:30 | s1 | 0 |
 | Parameters.cs:13:17:13:18 | M7 | Parameters.cs:13:27:13:28 | e1 | 0 |
-| Parameters.cs:35:32:35:39 | implicit conversion | Parameters.cs:35:54:35:54 | i | 0 |
-| Parameters.cs:36:32:36:39 | implicit conversion | Parameters.cs:36:57:36:57 | s | 0 |
+| Parameters.cs:36:32:36:39 | implicit conversion | Parameters.cs:36:54:36:54 | i | 0 |
+| Parameters.cs:37:32:37:39 | implicit conversion | Parameters.cs:37:57:37:57 | s | 0 |
 | Parameters.dll:0:0:0:0 | M1 | Parameters.dll:0:0:0:0 | a | 0 |
 | Parameters.dll:0:0:0:0 | M1 | Parameters.dll:0:0:0:0 | b | 1 |
 | Parameters.dll:0:0:0:0 | M1 | Parameters.dll:0:0:0:0 | c | 2 |
@@ -47,6 +47,7 @@ withDefaultValue
 | Parameters.cs:29:17:29:19 | M21 | Parameters.cs:29:76:29:80 | arg10 | 0 | Parameters.cs:29:21:29:80 | call to operator implicit conversion | - |
 | Parameters.cs:30:17:30:19 | M22 | Parameters.cs:30:27:30:31 | arg11 | 0 | Parameters.cs:30:35:30:35 | (...) ... | 0 |
 | Parameters.cs:31:17:31:19 | M23 | Parameters.cs:31:26:31:30 | arg12 | 0 | Parameters.cs:31:34:31:34 | (...) ... | 0 |
+| Parameters.cs:32:17:32:19 | M24 | Parameters.cs:32:65:32:69 | arg13 | 0 | Parameters.cs:32:21:32:69 | (...) ... | 7 |
 | Parameters.dll:0:0:0:0 | M2 | Parameters.dll:0:0:0:0 | b | 1 | Parameters.dll:0:0:0:0 | default | null |
 | Parameters.dll:0:0:0:0 | M2 | Parameters.dll:0:0:0:0 | c | 2 | Parameters.dll:0:0:0:0 | "default string" | default string |
 | Parameters.dll:0:0:0:0 | M3 | Parameters.dll:0:0:0:0 | a | 0 | Parameters.dll:0:0:0:0 | 1 | 1 |
@@ -78,6 +79,7 @@ withDefaultValue
 | Parameters.dll:0:0:0:0 | M21 | Parameters.dll:0:0:0:0 | arg10 | 0 | Parameters.dll:0:0:0:0 | call to operator implicit conversion | - |
 | Parameters.dll:0:0:0:0 | M22 | Parameters.dll:0:0:0:0 | arg11 | 0 | Parameters.dll:0:0:0:0 | (...) ... | 0 |
 | Parameters.dll:0:0:0:0 | M23 | Parameters.dll:0:0:0:0 | arg12 | 0 | Parameters.dll:0:0:0:0 | (...) ... | 0 |
+| Parameters.dll:0:0:0:0 | M24 | Parameters.dll:0:0:0:0 | arg13 | 0 | Parameters.dll:0:0:0:0 | (...) ... | 7 |
 dateTimeDefaults
 | Parameters.cs:22:17:22:19 | M14 | Parameters.cs:22:64:22:67 | arg4 | Parameters.cs:22:21:22:67 | object creation of type DateTime | DateTime(long) | 14 |
 | Parameters.cs:23:17:23:19 | M15 | Parameters.cs:23:68:23:71 | arg5 | Parameters.cs:23:21:23:71 | object creation of type DateTime | DateTime(long) | 10001 |

csharp/ql/test/library-tests/parameters/Parameters.expected

@@ -41,4 +41,3 @@ extractorMessages
 | errors.cs:91:45:91:45 | Failed to resolve name |
 | errors.cs:92:45:92:45 | Failed to determine type |
 | errors.cs:92:45:92:45 | Failed to resolve name |
-| file://:0:0:0:0 | Extracting default argument value 'object RecordNumber = default' instead of 'object RecordNumber = -1'. The latter is not supported in C#. |