Only cast for boxing when it's not implicit - fixes #1071

But since this removes some casts, do still ensure that predefined cast expressions always cast since otherwise casting to T via object gets broken

CHANGELOG.md

@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 * Conversion of explicit interface implementations now converts optional parameters [#1062](https://github.com/icsharpcode/CodeConverter/issues/1062)
 * Constant chars are converted to constant strings where needed
 * Select case for a mixture of strings and characters converts correctly [#1062](https://github.com/icsharpcode/CodeConverter/issues/1062)
+* Implicit boxing conversion converted correctly to no-op [#1071](https://github.com/icsharpcode/CodeConverter/issues/1071)
 
 ### C# -> VB
 

CodeConverter/CSharp/ExpressionNodeVisitor.cs

@@ -291,7 +291,7 @@ public override async Task<CSharpSyntaxNode> VisitPredefinedCastExpression(VBasi
                     SyntaxFactory.Argument(expressionSyntax))));
         }
 
-        var withConversion = CommonConversions.TypeConversionAnalyzer.AddExplicitConversion(node.Expression, expressionSyntax, false, false, forceTargetType: _semanticModel.GetTypeInfo(node).Type);
+        var withConversion = CommonConversions.TypeConversionAnalyzer.AddExplicitConversion(node.Expression, expressionSyntax, false, true, forceTargetType: _semanticModel.GetTypeInfo(node).Type);
         return node.ParenthesizeIfPrecedenceCouldChange(withConversion); // Use context of outer node, rather than just its exprssion, as the above method call would do if allowed to add parenthesis
     }
 

CodeConverter/CSharp/TypeConversionAnalyzer.cs

@@ -311,7 +311,7 @@ private ITypeSymbol GetCSType(ITypeSymbol vbType, VBSyntax.ExpressionSyntax vbNo
         } else if (vbConversion.IsNumeric && (csConversion.IsNumeric || nullableVbConvertedType.IsEnumType()) && isConvertFractionalToInt) {
             typeConversionKind = TypeConversionKind.FractionalNumberRoundThenCast;
             return true;
-        } else if (csConversion.IsExplicit && csConversion.IsEnumeration || csConversion.IsBoxing) {
+        } else if (csConversion is {IsExplicit: true, IsEnumeration: true} or {IsBoxing: true, IsImplicit: false}) {
             typeConversionKind = TypeConversionKind.NonDestructiveCast;
             return true;
         } else if (vbConversion.IsNumeric && csConversion.IsNumeric) {

Tests/CSharp/ExpressionTests/BinaryExpressionTests.cs

@@ -668,7 +668,7 @@ private object TestMethod()
     {
         bool? var1 = default;
         bool? var2 = default;
-        return (object)(var1.GetValueOrDefault() ? true : !var2 is not { } arg1 ? null : arg1 ? true : var1);
+        return var1.GetValueOrDefault() ? true : !var2 is not { } arg1 ? null : arg1 ? true : var1;
     }
 }");
     }

Tests/CSharp/ExpressionTests/ExpressionTests.cs

@@ -80,6 +80,33 @@ public bool IsPointWithinBoundaryBox(double dblLat, double dblLon, object boundb
 }");
     }
 
+    [Fact]
+    public async Task DynamicAccessAsync()
+    {
+        await TestConversionVisualBasicToCSharpAsync(@"Option Strict Off ' Directive gets removed
+
+Public Class TestDynamicUsage
+    Property Prop As Integer
+
+    Sub S()
+        Dim o As Object
+        o = New TestDynamicUsage
+        o.Prop = 1 'Must not cast to object here
+    End Sub
+End Class", @"
+public partial class TestDynamicUsage
+{
+    public int Prop { get; set; }
+
+    public void S()
+    {
+        object o;
+        o = new TestDynamicUsage();
+        ((dynamic)o).Prop = 1; // Must not cast to object here
+    }
+}");
+    }
+
     [Fact]
     public async Task ConversionOfNotUsesParensIfNeededAsync()
     {
@@ -267,12 +294,11 @@ public partial class VisualBasicClass
     public void Rounding()
     {
         object o = 3.0f;
-        var x = Math.Round(o, (object)2);
+        var x = Math.Round(o, 2);
     }
 }
-2 target compilation errors:
-CS1503: Argument 1: cannot convert from 'object' to 'double'
-CS1503: Argument 2: cannot convert from 'object' to 'int'");
+1 target compilation errors:
+CS1503: Argument 1: cannot convert from 'object' to 'double'");
     }
 
     [Fact]

Tests/CSharp/MissingSemanticModelInfo/ExpressionTests.cs

@@ -391,7 +391,7 @@ public void Test()
     {
         SomeUnknownType x = default;
         int y = 3;
-        if (x == null || (object)y == null)
+        if (x == null || y == null)
         {
 
         }