Improve null case handling in MatchLegacySwitchOnStringWithDict

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

@@ -104,6 +104,7 @@
     <None Include="TestCases\ILPretty\Issue1922.il" />
     <None Include="TestCases\ILPretty\Issue1918.il" />
     <None Include="TestCases\ILPretty\Issue2104.il" />
+    <None Include="TestCases\ILPretty\Issue3421.il" />
     <None Include="TestCases\ILPretty\WeirdEnums.il" />
     <None Include="TestCases\ILPretty\ConstantBlobs.il" />
     <None Include="TestCases\ILPretty\CS1xSwitch_Debug.il" />
@@ -129,6 +130,7 @@
     <Compile Include="Output\InsertParenthesesVisitorTests.cs" />
     <Compile Include="ProjectDecompiler\TargetFrameworkTests.cs" />
     <Compile Include="TestAssemblyResolver.cs" />
+    <Compile Include="TestCases\ILPretty\Issue3421.cs" />
     <Compile Include="TestCases\ILPretty\MonoFixed.cs" />
     <Compile Include="TestCases\Pretty\Comparisons.cs" />
     <None Include="TestCases\VBPretty\VBAutomaticEvents.vb" />

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -207,6 +207,12 @@ public async Task Issue2443()
 			await Run();
 		}
 
+		[Test]
+		public async Task Issue3421()
+		{
+			await Run();
+		}
+
 		[Test]
 		public async Task Issue2260SwitchString()
 		{

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue3421.cs

@@ -0,0 +1,26 @@
+internal class Issue3421
+{
+	private string name;
+	private object value;
+
+	public virtual void SetValue(object value)
+	{
+		switch (name)
+		{
+			case "##Name##":
+				return;
+			case "##Value##":
+				this.value = value;
+				return;
+			case "##InnerText##":
+				this.value = value.ToString();
+				return;
+			case null:
+				return;
+		}
+		if (this.value == null)
+		{
+			this.value = "";
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue3421.il

@@ -0,0 +1,116 @@
+#define CORE_ASSEMBLY "System.Runtime"
+
+.assembly extern CORE_ASSEMBLY
+{
+  .publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A )                         // .?_....:
+  .ver 4:0:0:0
+}
+
+.class private auto ansi beforefieldinit Issue3421
+    extends [CORE_ASSEMBLY]System.Object
+{
+    // Fields
+    .field private string name
+    .field private object 'value'
+    .field private static class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32> '<>f__switch$map1D'
+    .custom instance void [CORE_ASSEMBLY]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (
+        01 00 00 00
+    )
+
+    // Methods
+    .method public hidebysig virtual 
+        instance void SetValue (
+            object 'value'
+        ) cil managed 
+    {
+        // Method begins at RVA 0x2050
+        // Header size: 12
+        // Code size: 180 (0xb4)
+        .maxstack 27
+        .locals init (
+            [0] string,
+            [1] class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32>,
+            [2] int32
+        )
+
+        IL_0000: ldarg.0
+        IL_0001: ldfld string Issue3421::name
+        IL_0006: stloc.0
+        IL_0007: ldloc.0
+        IL_0008: brfalse IL_0093
+
+        IL_000d: ldsfld class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32> Issue3421::'<>f__switch$map1D'
+        IL_0012: brtrue IL_0048
+
+        IL_0017: ldc.i4.3
+        IL_0018: newobj instance void class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32>::.ctor(int32)
+        IL_001d: stloc.1
+        IL_001e: ldloc.1
+        IL_001f: ldstr "##Name##"
+        IL_0024: ldc.i4.0
+        IL_0025: callvirt instance void class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0, !1)
+        IL_002a: ldloc.1
+        IL_002b: ldstr "##Value##"
+        IL_0030: ldc.i4.1
+        IL_0031: callvirt instance void class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0, !1)
+        IL_0036: ldloc.1
+        IL_0037: ldstr "##InnerText##"
+        IL_003c: ldc.i4.2
+        IL_003d: callvirt instance void class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0, !1)
+        IL_0042: ldloc.1
+        IL_0043: stsfld class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32> Issue3421::'<>f__switch$map1D'
+
+        IL_0048: ldsfld class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32> Issue3421::'<>f__switch$map1D'
+        IL_004d: ldloc.0
+        IL_004e: ldloca.s 2
+        IL_0050: callvirt instance bool class [CORE_ASSEMBLY]System.Collections.Generic.Dictionary`2<string, int32>::TryGetValue(!0, !1&)
+        IL_0055: brfalse IL_0098
+
+        IL_005a: ldloc.2
+        IL_005b: switch (IL_0071, IL_0076, IL_0082)
+
+        IL_006c: br IL_0098
+
+        IL_0071: br IL_00b3
+
+        IL_0076: ldarg.0
+        IL_0077: ldarg.1
+        IL_0078: stfld object Issue3421::'value'
+        IL_007d: br IL_00b3
+
+        IL_0082: ldarg.0
+        IL_0083: ldarg.1
+        IL_0084: callvirt instance string [CORE_ASSEMBLY]System.Object::ToString()
+        IL_0089: stfld object Issue3421::'value'
+        IL_008e: br IL_00b3
+
+        IL_0093: br IL_00b3
+
+        IL_0098: ldarg.0
+        IL_0099: ldfld object Issue3421::'value'
+        IL_009e: brtrue IL_00ae
+
+        IL_00a3: ldarg.0
+        IL_00a4: ldstr ""
+        IL_00a9: stfld object Issue3421::'value'
+
+        IL_00ae: br IL_00b3
+
+        IL_00b3: ret
+    } // end of method Issue3421::SetValue
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor () cil managed 
+    {
+        // Method begins at RVA 0x2110
+        // Header size: 1
+        // Code size: 8 (0x8)
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [CORE_ASSEMBLY]System.Object::.ctor()
+        IL_0006: nop
+        IL_0007: ret
+    } // end of method Issue3421::.ctor
+
+} // end of class Issue3421

ICSharpCode.Decompiler/IL/Transforms/SwitchOnStringTransform.cs

@@ -668,13 +668,20 @@ bool MatchLegacySwitchOnStringWithDict(InstructionCollection<ILInstruction> inst
 			if (!FixCasesWithoutValue(sections, stringValues))
 				return false;
 			// switch contains case null:
-			if (nullValueCaseBlock != defaultBlock)
+			if (nullValueCaseBlock != null && nullValueCaseBlock != defaultBlock)
 			{
 				if (!AddNullSection(sections, stringValues, nullValueCaseBlock))
 				{
 					return false;
 				}
 			}
+			else if (leaveContainer != null && !defaultBlockJump.MatchLeave(leaveContainer))
+			{
+				if (!AddNullSection(sections, stringValues, (Leave)exitBlockJump))
+				{
+					return false;
+				}
+			}
 			context.Step(nameof(MatchLegacySwitchOnStringWithDict), instructions[i]);
 			bool keepAssignmentBefore = false;
 			if (switchValueVar.LoadCount > 2 || switchValue == null)
@@ -741,6 +748,11 @@ bool HasLabel(SwitchSection section)
 		}
 
 		bool AddNullSection(List<SwitchSection> sections, List<(string Value, int Index)> stringValues, Block nullValueCaseBlock)
+		{
+			return AddNullSection(sections, stringValues, new Branch(nullValueCaseBlock));
+		}
+
+		bool AddNullSection(List<SwitchSection> sections, List<(string Value, int Index)> stringValues, ILInstruction body)
 		{
 			var label = new LongSet(stringValues.Max(item => item.Index) + 1);
 			var possibleConflicts = sections.Where(sec => sec.Labels.Overlaps(label)).ToArray();
@@ -753,7 +765,7 @@ bool AddNullSection(List<SwitchSection> sections, List<(string Value, int Index)
 				possibleConflicts[0].Labels = possibleConflicts[0].Labels.ExceptWith(label);
 			}
 			stringValues.Add((null, (int)label.Values.First()));
-			sections.Add(new SwitchSection() { Labels = label, Body = new Branch(nullValueCaseBlock) });
+			sections.Add(new SwitchSection() { Labels = label, Body = body });
 			return true;
 		}