Fix #646: VB-compilers 'For Each In' is not recognized as foreach during decompilation

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

@@ -62,6 +62,7 @@
     <Compile Include="TestCases\Correctness\TrickyTypes.cs" />
     <Compile Include="TestCases\Correctness\Using.cs" />
     <Compile Include="TestCases\ILPretty\Issue379.cs" />
+    <None Include="TestCases\ILPretty\Issue646.cs" />
     <Compile Include="TestCases\Pretty\Async.cs" />
     <Compile Include="TestCases\Pretty\CheckedUnchecked.cs" />
     <Compile Include="TestCases\Pretty\Generics.cs" />
@@ -115,6 +116,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <None Include="TestCases\ILPretty\Issue646.il" />
     <None Include="TestCases\Pretty\HelloWorld.il">
       <DependentUpon>HelloWorld.cs</DependentUpon>
     </None>

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -36,6 +36,12 @@ namespace ICSharpCode.Decompiler.Tests
 			Run();
 		}
 
+		[Test]
+		public void Issue646()
+		{
+			Run();
+		}
+
 		void Run([CallerMemberName] string testName = null)
 		{
 			var ilFile = Path.Combine(TestCasePath, testName + ".il");

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue646.cs

@@ -0,0 +1,20 @@
+using Microsoft.VisualBasic.CompilerServices;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.ILPretty
+{
+	[StandardModule]
+	internal sealed class Issue646
+	{
+		[STAThread]
+		public static void Main()
+		{
+			List<string> list = new List<string>();
+			foreach (string item in list) {
+				Debug.WriteLine(item);
+			}
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue646.il

@@ -0,0 +1,93 @@
+// 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 extern System
+{
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )                         // .z\V.4..
+  .ver 4:0:0:0
+}
+.assembly extern Microsoft.VisualBasic
+{
+  .publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A )                         // .?_....:
+  .ver 10:0:0:0
+}
+.assembly ConsoleApp11
+{
+  .ver 1:0:0:0
+}
+.module ConsoleApp11.exe
+// MVID: {B973FCD6-A9C4-48A9-8291-26DDC248E208}
+.imagebase 0x00400000
+.file alignment 0x00000200
+.stackreserve 0x00100000
+.subsystem 0x0003       // WINDOWS_CUI
+.corflags 0x00020003    //  ILONLY 32BITPREFERRED
+// Image base: 0x000001C4B6C90000
+
+.class private auto ansi sealed ICSharpCode.Decompiler.Tests.TestCases.ILPretty.Issue646
+	extends [mscorlib]System.Object
+{
+	.custom instance void [Microsoft.VisualBasic]Microsoft.VisualBasic.CompilerServices.StandardModuleAttribute::.ctor() = (
+		01 00 00 00
+	)
+	// Methods
+	.method public static 
+		void Main () cil managed 
+	{
+		.custom instance void [mscorlib]System.STAThreadAttribute::.ctor() = (
+			01 00 00 00
+		)
+		// Method begins at RVA 0x21b4
+		// Code size 61 (0x3d)
+		.maxstack 1
+		.entrypoint
+		.locals init (
+			[0] class [mscorlib]System.Collections.Generic.List`1<string>,
+			[1] valuetype [mscorlib]System.Collections.Generic.List`1/Enumerator<string>,
+			[2] string,
+			[3] bool
+		)
+
+		IL_0000: nop
+		IL_0001: newobj instance void class [mscorlib]System.Collections.Generic.List`1<string>::.ctor()
+		IL_0006: stloc.0
+		.try
+		{
+			IL_0007: ldloc.0
+			IL_0008: callvirt instance valuetype [mscorlib]System.Collections.Generic.List`1/Enumerator<!0> class [mscorlib]System.Collections.Generic.List`1<string>::GetEnumerator()
+			IL_000d: stloc.1
+			IL_000e: br.s IL_0020
+			// loop start (head: IL_0020)
+				IL_0010: ldloca.s 1
+				IL_0012: call instance !0 valuetype [mscorlib]System.Collections.Generic.List`1/Enumerator<string>::get_Current()
+				IL_0017: stloc.2
+				IL_0018: ldloc.2
+				IL_0019: call void [System]System.Diagnostics.Debug::WriteLine(string)
+				IL_001e: nop
+				IL_001f: nop
+
+				IL_0020: ldloca.s 1
+				IL_0022: call instance bool valuetype [mscorlib]System.Collections.Generic.List`1/Enumerator<string>::MoveNext()
+				IL_0027: stloc.3
+				IL_0028: ldloc.3
+				IL_0029: brtrue.s IL_0010
+			// end loop
+
+			IL_002b: leave.s IL_003c
+		} // end .try
+		finally
+		{
+			IL_002d: ldloca.s 1
+			IL_002f: constrained. valuetype [mscorlib]System.Collections.Generic.List`1/Enumerator<string>
+			IL_0035: callvirt instance void [mscorlib]System.IDisposable::Dispose()
+			IL_003a: nop
+			IL_003b: endfinally
+		} // end handler
+
+		IL_003c: ret
+	} // end of method Module1::Main
+
+} // end of class ConsoleApp11.Module1

ICSharpCode.Decompiler/IL/Transforms/UsingTransform.cs

@@ -34,7 +34,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			if (!context.Settings.UsingStatement) return;
 			this.context = context;
 			for (int i = block.Instructions.Count - 1; i >= 0; i--) {
-				if (!TransformUsing(block, i))
+				if (!TransformUsing(block, i) && !TransformUsingVB(block, i))
 					continue;
 				// This happens in some cases:
 				// Use correct index after transformation.
@@ -91,6 +91,55 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			return true;
 		}
 
+		/// <summary>
+		/// .try BlockContainer {
+		///		Block IL_0003(incoming: 1) {
+		///			stloc obj(resourceExpression)
+		///			call WriteLine(ldstr "using (null)")
+		///			leave IL_0003(nop)
+		///		}
+		///	} finally BlockContainer {
+		///		Block IL_0012(incoming: 1) {
+		///			if (comp(ldloc obj != ldnull)) Block IL_001a  {
+		///				callvirt Dispose(ldnull)
+		///			}
+		///			leave IL_0012(nop)
+		///		}
+		/// }
+		/// leave IL_0000(nop)
+		/// =>
+		/// using (resourceExpression) {
+		///		BlockContainer {
+		///			Block IL_0003(incoming: 1) {
+		///				call WriteLine(ldstr "using (null)")
+		///				leave IL_0003(nop)
+		///			}
+		///		}
+		/// }
+		/// </summary>
+		bool TransformUsingVB(Block block, int i)
+		{
+			if (!(block.Instructions[i] is TryFinally tryFinally))
+				return false;
+			if (!(tryFinally.TryBlock is BlockContainer tryContainer && tryContainer.EntryPoint.Instructions.FirstOrDefault() is StLoc storeInst))
+				return false;
+			if (!(storeInst.Value.MatchLdNull() || CheckResourceType(storeInst.Variable.Type)))
+				return false;
+			if (storeInst.Variable.LoadInstructions.Any(ld => !ld.IsDescendantOf(tryFinally)))
+				return false;
+			if (storeInst.Variable.AddressInstructions.Any(la => !la.IsDescendantOf(tryFinally) || (la.IsDescendantOf(tryFinally.TryBlock) && !ILInlining.IsUsedAsThisPointerInCall(la))))
+				return false;
+			if (storeInst.Variable.StoreInstructions.OfType<ILInstruction>().Any(st => st != storeInst))
+				return false;
+			if (!(tryFinally.FinallyBlock is BlockContainer container) || !MatchDisposeBlock(container, storeInst.Variable, storeInst.Value.MatchLdNull()))
+				return false;
+			context.Step("UsingTransformVB", tryFinally);
+			storeInst.Variable.Kind = VariableKind.UsingLocal;
+			tryContainer.EntryPoint.Instructions.RemoveAt(0);
+			block.Instructions[i] = new UsingInstruction(storeInst.Variable, storeInst.Value, tryFinally.TryBlock);
+			return true;
+		}
+
 		bool CheckResourceType(IType type)
 		{
 			// non-generic IEnumerator does not implement IDisposable.