Fix CS0162 warning about unreachable code (#1492)

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -996,6 +996,8 @@ namespace CppSharp.Generators.CSharp
                 WriteLine($@"throw new MissingMethodException(""Method {
                     property.Name} missing from explicit specialization {
                     @class.Visit(TypePrinter)}."");");
+
+                AddBlock(new Block(BlockKind.Unreachable));
                 return;
             }
             property = actualProperty;
@@ -1325,6 +1327,8 @@ namespace CppSharp.Generators.CSharp
                 WriteLine($@"throw new MissingMethodException(""Method {
                     property.Name} missing from explicit specialization {
                     @class.Visit(TypePrinter)}."");");
+
+                AddBlock(new Block(BlockKind.Unreachable));
                 return;
             }
             GenerateFunctionInProperty(@class, actualProperty.GetMethod, actualProperty,
@@ -2633,6 +2637,8 @@ internal static{(@new ? " new" : string.Empty)} {printedClass} __GetInstance({Ty
                     WriteLine($@"throw new MissingMethodException(""Method {
                         method.Name} missing from explicit specialization {
                         @class.Visit(TypePrinter)}."");");
+
+                    AddBlock(new Block(BlockKind.Unreachable));
                     return;
                 }
                 if (specializedMethod.Ignore)
@@ -2640,6 +2646,8 @@ internal static{(@new ? " new" : string.Empty)} {printedClass} __GetInstance({Ty
                     WriteLine($@"throw new MissingMethodException(""Method {
                         method.Name} ignored in specialization {
                         @class.Visit(TypePrinter)}."");");
+
+                    AddBlock(new Block(BlockKind.Unreachable));
                     return;
                 }
 

src/Generator/Generators/CSharp/CSharpSourcesExtensions.cs

@@ -105,11 +105,13 @@ namespace CppSharp.Generators.CSharp
                 foreach (var specialization in @class.Specializations.Where(s => s.IsGenerated))
                 {
                     WriteTemplateSpecializationCheck(gen, @class, specialization);
+                    gen.PushBlock(BlockKind.Block);
                     gen.WriteOpenBraceAndIndent();
                     generate(specialization);
-                    if (isVoid)
+                    if (isVoid && !gen.ActiveBlock.FindBlocks(BlockKind.Unreachable).Any())
                         gen.WriteLine("return;");
                     gen.UnindentAndWriteCloseBrace();
+                    gen.PopBlock();
                 }
                 ThrowException(gen, @class);
             }

src/Generator/Utils/BlockGenerator.cs

@@ -17,6 +17,7 @@ namespace CppSharp
     public enum BlockKind
     {
         Unknown,
+        Block,
         BlockComment,
         InlineComment,
         Header,
@@ -36,6 +37,7 @@ namespace CppSharp
         Event,
         Variable,
         Property,
+        Unreachable,
         Field,
         VTableDelegate,
         Region,