Fix #1605: Inline ref locals more aggressively; this is necessary for VB compound assignments.

ICSharpCode.Decompiler.Tests/Helpers/Tester.VB.cs

@@ -56,10 +56,10 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 				var provider = new VBCodeProvider(new Dictionary<string, string> { { "CompilerVersion", "v4.0" } });
 				CompilerParameters options = new CompilerParameters();
 				options.GenerateExecutable = !flags.HasFlag(CompilerOptions.Library);
-				options.CompilerOptions = "/o" + (flags.HasFlag(CompilerOptions.Optimize) ? "+" : "-");
+				options.CompilerOptions = "/optimize" + (flags.HasFlag(CompilerOptions.Optimize) ? "+" : "-");
 				options.CompilerOptions += (flags.HasFlag(CompilerOptions.UseDebug) ? " /debug" : "");
 				options.CompilerOptions += (flags.HasFlag(CompilerOptions.Force32Bit) ? " /platform:anycpu32bitpreferred" : "");
-				options.CompilerOptions += "/optioninfer+ /optionexplicit+";
+				options.CompilerOptions += " /optioninfer+ /optionexplicit+";
 				if (preprocessorSymbols.Count > 0) {
 					options.CompilerOptions += " /d:" + string.Join(",", preprocessorSymbols.Select(p => $"{p.Key}={p.Value}"));
 				}

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

@@ -81,6 +81,7 @@
     <Compile Include="DisassemblerPrettyTestRunner.cs" />
     <Compile Include="TestCases\ILPretty\ConstantBlobs.cs" />
     <Compile Include="TestCases\Pretty\OutVariables.cs" />
+    <None Include="TestCases\VBPretty\VBCompoundAssign.cs" />
     <None Include="TestCases\ILPretty\Issue1145.cs" />
     <Compile Include="TestCases\ILPretty\Issue1157.cs" />
     <None Include="TestCases\ILPretty\Unsafe.cs" />
@@ -243,6 +244,7 @@
     <None Include="TestCases\ILPretty\Issue379.il" />
     <None Include="TestCases\ILPretty\Issue982.il" />
     <None Include="TestCases\Pretty\Readme.txt" />
+    <None Include="TestCases\VBPretty\VBCompoundAssign.vb" />
     <None Include="TestCases\VBPretty\Async.vb" />
   </ItemGroup>
 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/RefLocalsAndReturns.cs

@@ -193,7 +193,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		{
 			ref NormalStruct @ref = ref GetRef<NormalStruct>();
 			RefReassignment(ref @ref);
-			@ref = ref GetRef<NormalStruct>();
+			if (s.GetHashCode() == 0) {
+				@ref = ref GetRef<NormalStruct>();
+			}
 			RefReassignment(ref @ref.GetHashCode() == 4 ? ref @ref : ref s);
 		}
 

ICSharpCode.Decompiler.Tests/TestCases/VBPretty/.gitignore

@@ -0,0 +1 @@
+*.dll

ICSharpCode.Decompiler.Tests/TestCases/VBPretty/VBCompoundAssign.cs

@@ -0,0 +1,20 @@
+using Microsoft.VisualBasic;
+using Microsoft.VisualBasic.CompilerServices;
+
+[StandardModule]
+internal sealed class VBCompoundAssign
+{
+	public static double[] Sum3(int[] v)
+	{
+		double[] array = new double[4];
+		int num = Information.UBound(v);
+		checked {
+			for (int i = 0; i <= num; i += 3) {
+				array[0] += v[i];
+				array[1] += v[i + 1];
+				array[2] += v[i + 2];
+			}
+			return array;
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/VBPretty/VBCompoundAssign.vb

@@ -0,0 +1,14 @@
+Imports System
+Imports Microsoft.VisualBasic
+
+Module VBCompoundAssign
+    Function Sum3(v As Int32()) As Double()
+        Dim arr(3) As Double
+        For i = 0 To UBound(v) Step 3
+            arr(0) += v(i)
+            arr(1) += v(i + 1)
+            arr(2) += v(i + 2)
+        Next
+        Return arr
+    End Function
+End Module

ICSharpCode.Decompiler.Tests/VBPrettyTestRunner.cs

@@ -61,17 +61,27 @@ namespace ICSharpCode.Decompiler.Tests
 		};
 
 		[Test, Ignore("Implement VB async/await")]
-		public void Async([ValueSource("defaultOptions")] CompilerOptions options)
+		public void Async([ValueSource(nameof(defaultOptions))] CompilerOptions options)
 		{
 			Run(options: options);
 		}
 
+		[Test] // TODO: legacy VB compound assign
+		public void VBCompoundAssign([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions options)
+		{
+			Run(options: options | CompilerOptions.Library);
+		}
+
 		void Run([CallerMemberName] string testName = null, CompilerOptions options = CompilerOptions.UseDebug, DecompilerSettings settings = null)
 		{
 			var vbFile = Path.Combine(TestCasePath, testName + ".vb");
 			var csFile = Path.Combine(TestCasePath, testName + ".cs");
+			var exeFile = Path.Combine(TestCasePath, testName) + Tester.GetSuffix(options) + ".exe";
+			if (options.HasFlag(CompilerOptions.Library)) {
+				exeFile = Path.ChangeExtension(exeFile, ".dll");
+			}
 
-			var executable = Tester.CompileVB(vbFile, options);
+			var executable = Tester.CompileVB(vbFile, options | CompilerOptions.ReferenceVisualBasic, exeFile);
 			var decompiled = Tester.DecompileCSharp(executable.PathToAssembly, settings);
 
 			CodeAssert.FilesAreEqual(csFile, decompiled);

ICSharpCode.Decompiler/IL/Transforms/ILInlining.cs

@@ -404,7 +404,13 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					}
 					break;
 			}
-			
+			if (inlinedExpression.ResultType == StackType.Ref) {
+				// VB likes to use ref locals for compound assignment
+				// (the C# compiler uses ref stack slots instead).
+				// We want to avoid unnecessary ref locals, so we'll always inline them if possible.
+				return true;
+			}
+
 			var parent = loadInst.Parent;
 			if (NullableLiftingTransform.MatchNullableCtor(parent, out _, out _)) {
 				// inline into nullable ctor call in lifted operator