Add an option to not transform Activator.CreateInstance<T>() to new T()

ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -152,6 +152,8 @@
     <Compile Include="TestCases\Pretty\Issue3442.cs" />
     <Compile Include="TestCases\Pretty\Issue3483.cs" />
     <Compile Include="TestCases\Pretty\PointerArithmetic.cs" />
+    <Compile Include="TestCases\Ugly\NoNewOfT.cs" />
+    <None Include="TestCases\Ugly\NoNewOfT.Expected.cs" />
     <Compile Include="TestCases\Pretty\ParamsCollections.cs" />
     <None Include="TestCases\VBPretty\VBAutomaticEvents.vb" />
     <Compile Include="TestCases\VBPretty\VBAutomaticEvents.cs" />

ICSharpCode.Decompiler.Tests/TestCases/Ugly/NoNewOfT.Expected.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Ugly
+{
+	internal class NoNewOfT<TOnType> where TOnType : new()
+	{
+		public static TOnType CreateTOnType()
+		{
+#if !ROSLYN
+#if OPT
+			if (default(TOnType) != null)
+			{
+				return default(TOnType);
+			}
+			return Activator.CreateInstance<TOnType>();
+#else
+			return (default(TOnType) == null) ? Activator.CreateInstance<TOnType>() : default(TOnType);
+#endif
+#else
+			return Activator.CreateInstance<TOnType>();
+#endif
+		}
+
+		public static T CreateUnconstrainedT<T>() where T : new()
+		{
+#if !ROSLYN
+#if OPT
+			if (default(T) != null)
+			{
+				return default(T);
+			}
+			return Activator.CreateInstance<T>();
+#else
+			return (default(T) == null) ? Activator.CreateInstance<T>() : default(T);
+#endif
+#else
+			return Activator.CreateInstance<T>();
+#endif
+		}
+
+		public static T CreateClassT<T>() where T : class, new()
+		{
+			return Activator.CreateInstance<T>();
+		}
+
+		public static T CollectionInitializer<T>() where T : IList<int>, new()
+		{
+#if ROSLYN
+			T result = Activator.CreateInstance<T>();
+			result.Add(1);
+			result.Add(2);
+			result.Add(3);
+			result.Add(4);
+			result.Add(5);
+			return result;
+#else
+			T val = ((default(T) == null) ? Activator.CreateInstance<T>() : default(T));
+			val.Add(1);
+			val.Add(2);
+			val.Add(3);
+			val.Add(4);
+			val.Add(5);
+			return val;
+#endif
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/Ugly/NoNewOfT.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Ugly
+{
+	internal class NoNewOfT<TOnType> where TOnType : new()
+	{
+		public static TOnType CreateTOnType()
+		{
+			return new TOnType();
+		}
+
+		public static T CreateUnconstrainedT<T>() where T : new()
+		{
+			return new T();
+		}
+
+		public static T CreateClassT<T>() where T : class, new()
+		{
+			return new T();
+		}
+
+		public static T CollectionInitializer<T>() where T : IList<int>, new()
+		{
+			return new T() { 1, 2, 3, 4, 5 };
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/Ugly/NoNewOfT.il

@@ -0,0 +1,176 @@
+
+//  .NET IL Disassembler.  Version 9.0.4
+
+
+
+// Metadata version: v4.0.30319
+.assembly extern mscorlib
+{
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )                         // .z\V.4..
+  .ver 4:0:0:0
+}
+.assembly tmpvpdwr1
+{
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilationRelaxationsAttribute::.ctor(int32) = ( 01 00 08 00 00 00 00 00 ) 
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::.ctor() = ( 01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
+                                                                                                             63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01 )       // ceptionThrows.
+  .permissionset reqmin
+             = {[mscorlib]System.Security.Permissions.SecurityPermissionAttribute = {property bool 'SkipVerification' = bool(true)}}
+  .hash algorithm 0x00008004
+  .ver 0:0:0:0
+}
+.module tmpvpdwr1.tmp
+// MVID: {8447adbb-757d-4626-b7b7-846d745d90d0}
+.custom instance void [mscorlib]System.Security.UnverifiableCodeAttribute::.ctor() = ( 01 00 00 00 ) 
+.imagebase 0x10000000
+.file alignment 0x00000200
+.stackreserve 0x00100000
+.subsystem 0x0003       // WINDOWS_CUI
+.corflags 0x00000001    //  ILONLY
+
+
+// =============== CLASS MEMBERS DECLARATION ===================
+
+.class private auto ansi beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.Ugly.NoNewOfT`1<.ctor TOnType>
+       extends [mscorlib]System.Object
+{
+  .method public hidebysig static !TOnType 
+          CreateTOnType() cil managed
+  {
+    // Code size       39 (0x27)
+    .maxstack  1
+    .locals init (!TOnType V_0,
+             !TOnType V_1)
+    IL_0000:  nop
+    IL_0001:  ldloca.s   V_1
+    IL_0003:  initobj    !TOnType
+    IL_0009:  ldloc.1
+    IL_000a:  box        !TOnType
+    IL_000f:  brfalse.s  IL_001c
+
+    IL_0011:  ldloca.s   V_1
+    IL_0013:  initobj    !TOnType
+    IL_0019:  ldloc.1
+    IL_001a:  br.s       IL_0021
+
+    IL_001c:  call       !!0 [mscorlib]System.Activator::CreateInstance<!TOnType>()
+    IL_0021:  nop
+    IL_0022:  stloc.0
+    IL_0023:  br.s       IL_0025
+
+    IL_0025:  ldloc.0
+    IL_0026:  ret
+  } // end of method NoNewOfT`1::CreateTOnType
+
+  .method public hidebysig static !!T  CreateUnconstrainedT<.ctor T>() cil managed
+  {
+    // Code size       39 (0x27)
+    .maxstack  1
+    .locals init (!!T V_0,
+             !!T V_1)
+    IL_0000:  nop
+    IL_0001:  ldloca.s   V_1
+    IL_0003:  initobj    !!T
+    IL_0009:  ldloc.1
+    IL_000a:  box        !!T
+    IL_000f:  brfalse.s  IL_001c
+
+    IL_0011:  ldloca.s   V_1
+    IL_0013:  initobj    !!T
+    IL_0019:  ldloc.1
+    IL_001a:  br.s       IL_0021
+
+    IL_001c:  call       !!0 [mscorlib]System.Activator::CreateInstance<!!0>()
+    IL_0021:  nop
+    IL_0022:  stloc.0
+    IL_0023:  br.s       IL_0025
+
+    IL_0025:  ldloc.0
+    IL_0026:  ret
+  } // end of method NoNewOfT`1::CreateUnconstrainedT
+
+  .method public hidebysig static !!T  CreateClassT<class .ctor T>() cil managed
+  {
+    // Code size       11 (0xb)
+    .maxstack  1
+    .locals init (!!T V_0)
+    IL_0000:  nop
+    IL_0001:  call       !!0 [mscorlib]System.Activator::CreateInstance<!!0>()
+    IL_0006:  stloc.0
+    IL_0007:  br.s       IL_0009
+
+    IL_0009:  ldloc.0
+    IL_000a:  ret
+  } // end of method NoNewOfT`1::CreateClassT
+
+  .method public hidebysig static !!T  CollectionInitializer<.ctor (class [mscorlib]System.Collections.Generic.IList`1<int32>) T>() cil managed
+  {
+    // Code size       106 (0x6a)
+    .maxstack  2
+    .locals init (!!T V_0,
+             !!T V_1,
+             !!T V_2)
+    IL_0000:  nop
+    IL_0001:  ldloca.s   V_2
+    IL_0003:  initobj    !!T
+    IL_0009:  ldloc.2
+    IL_000a:  box        !!T
+    IL_000f:  brfalse.s  IL_001c
+
+    IL_0011:  ldloca.s   V_2
+    IL_0013:  initobj    !!T
+    IL_0019:  ldloc.2
+    IL_001a:  br.s       IL_0021
+
+    IL_001c:  call       !!0 [mscorlib]System.Activator::CreateInstance<!!0>()
+    IL_0021:  nop
+    IL_0022:  stloc.0
+    IL_0023:  ldloc.0
+    IL_0024:  box        !!T
+    IL_0029:  ldc.i4.1
+    IL_002a:  callvirt   instance void class [mscorlib]System.Collections.Generic.ICollection`1<int32>::Add(!0)
+    IL_002f:  nop
+    IL_0030:  ldloc.0
+    IL_0031:  box        !!T
+    IL_0036:  ldc.i4.2
+    IL_0037:  callvirt   instance void class [mscorlib]System.Collections.Generic.ICollection`1<int32>::Add(!0)
+    IL_003c:  nop
+    IL_003d:  ldloc.0
+    IL_003e:  box        !!T
+    IL_0043:  ldc.i4.3
+    IL_0044:  callvirt   instance void class [mscorlib]System.Collections.Generic.ICollection`1<int32>::Add(!0)
+    IL_0049:  nop
+    IL_004a:  ldloc.0
+    IL_004b:  box        !!T
+    IL_0050:  ldc.i4.4
+    IL_0051:  callvirt   instance void class [mscorlib]System.Collections.Generic.ICollection`1<int32>::Add(!0)
+    IL_0056:  nop
+    IL_0057:  ldloc.0
+    IL_0058:  box        !!T
+    IL_005d:  ldc.i4.5
+    IL_005e:  callvirt   instance void class [mscorlib]System.Collections.Generic.ICollection`1<int32>::Add(!0)
+    IL_0063:  nop
+    IL_0064:  ldloc.0
+    IL_0065:  stloc.1
+    IL_0066:  br.s       IL_0068
+
+    IL_0068:  ldloc.1
+    IL_0069:  ret
+  } // end of method NoNewOfT`1::CollectionInitializer
+
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor() cil managed
+  {
+    // Code size       7 (0x7)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  call       instance void [mscorlib]System.Object::.ctor()
+    IL_0006:  ret
+  } // end of method NoNewOfT`1::.ctor
+
+} // end of class ICSharpCode.Decompiler.Tests.TestCases.Ugly.NoNewOfT`1
+
+
+// =============================================================
+
+// *********** DISASSEMBLY COMPLETE ***********************