Fix potential NRE in ILFunction.RegisterVariable()

ICSharpCode.Decompiler/IL/Instructions/ILFunction.cs

@@ -412,18 +412,7 @@ namespace ICSharpCode.Decompiler.IL
 
 		public ILVariable RegisterVariable(VariableKind kind, IType type, string? name = null)
 		{
-			return RegisterVariable(kind, type, type.GetStackType(), name);
-		}
-
-		public ILVariable RegisterVariable(VariableKind kind, StackType stackType, string? name = null)
-		{
-			var type = Method.Compilation.FindType(stackType.ToKnownTypeCode());
-			return RegisterVariable(kind, type, stackType, name);
-		}
-
-		ILVariable RegisterVariable(VariableKind kind, IType type, StackType stackType, string? name = null)
-		{
-			var variable = new ILVariable(kind, type, stackType);
+			var variable = new ILVariable(kind, type);
 			if (string.IsNullOrWhiteSpace(name))
 			{
 				name = "I_" + (helperVariableCount++);

ICSharpCode.Decompiler/IL/Instructions/ILInstruction.cs

@@ -24,6 +24,7 @@ using System.Diagnostics;
 using System.Threading;
 
 using ICSharpCode.Decompiler.IL.Patterns;
+using ICSharpCode.Decompiler.IL.Transforms;
 using ICSharpCode.Decompiler.TypeSystem;
 using ICSharpCode.Decompiler.Util;
 
@@ -899,9 +900,9 @@ namespace ICSharpCode.Decompiler.IL
 		/// If extraction is not possible, the ILAst is left unmodified and the function returns null.
 		/// May return null if extraction is not possible.
 		/// </summary>
-		public ILVariable Extract()
+		public ILVariable Extract(ILTransformContext context)
 		{
-			return Transforms.ExtractionContext.Extract(this);
+			return Transforms.ExtractionContext.Extract(this, context);
 		}
 
 		/// <summary>

ICSharpCode.Decompiler/IL/Transforms/FixLoneIsInst.cs

@@ -16,7 +16,6 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -63,7 +62,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			{
 				// Use extraction to turn isInst.Argument into a pure instruction, thus making the emulation possible
 				context.Step("FixLoneIsInst", isInst);
-				isInst.Argument.Extract();
+				isInst.Argument.Extract(context);
 			}
 		}
 	}

ICSharpCode.Decompiler/IL/Transforms/FixRemainingIncrements.cs

@@ -16,7 +16,6 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
@@ -73,7 +72,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				else
 				{
 					context.Step($"Fix {call.Method.Name} call at 0x{call.StartILOffset:x4} using new local", call);
-					var newVariable = call.Arguments[0].Extract();
+					var newVariable = call.Arguments[0].Extract(context);
 					if (newVariable == null)
 					{
 						Debug.Fail("Failed to extract argument of remaining increment/decrement");

ICSharpCode.Decompiler/IL/Transforms/ILExtraction.cs

@@ -21,6 +21,8 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 
+using ICSharpCode.Decompiler.TypeSystem;
+
 namespace ICSharpCode.Decompiler.IL.Transforms
 {
 	/// <summary>
@@ -33,6 +35,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		/// </summary>
 		readonly ILFunction Function;
 
+		readonly ILTransformContext context;
+
 		/// <summary>
 		/// Combined flags of all instructions being moved.
 		/// </summary>
@@ -47,17 +51,19 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		/// </summary>
 		readonly List<Func<ILInstruction>> MoveActions = new List<Func<ILInstruction>>();
 
-		ExtractionContext(ILFunction function)
+		ExtractionContext(ILFunction function, ILTransformContext context)
 		{
 			Debug.Assert(function != null);
 			this.Function = function;
+			this.context = context;
 		}
 
 		internal void RegisterMove(ILInstruction predecessor)
 		{
 			FlagsBeingMoved |= predecessor.Flags;
 			MoveActions.Add(delegate {
-				var v = Function.RegisterVariable(VariableKind.StackSlot, predecessor.ResultType);
+				var type = context.TypeSystem.FindType(predecessor.ResultType.ToKnownTypeCode());
+				var v = Function.RegisterVariable(VariableKind.StackSlot, type);
 				predecessor.ReplaceWith(new LdLoc(v));
 				return new StLoc(v, predecessor);
 			});
@@ -91,10 +97,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		/// 
 		/// May return null if extraction is not possible.
 		/// </summary>
-		public static ILVariable Extract(ILInstruction instToExtract)
+		public static ILVariable Extract(ILInstruction instToExtract, ILTransformContext context)
 		{
 			var function = instToExtract.Ancestors.OfType<ILFunction>().First();
-			ExtractionContext ctx = new ExtractionContext(function);
+			ExtractionContext ctx = new ExtractionContext(function, context);
 			ctx.FlagsBeingMoved = instToExtract.Flags;
 			ILInstruction inst = instToExtract;
 			while (inst != null)
@@ -113,8 +119,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				{
 					// We've reached the target block, and extraction is possible all the way.
 					int insertIndex = inst.ChildIndex;
+					var type = context.TypeSystem.FindType(instToExtract.ResultType.ToKnownTypeCode());
 					// Move instToExtract itself:
-					var v = function.RegisterVariable(VariableKind.StackSlot, instToExtract.ResultType);
+					var v = function.RegisterVariable(VariableKind.StackSlot, type);
 					instToExtract.ReplaceWith(new LdLoc(v));
 					block.Instructions.Insert(insertIndex, new StLoc(v, instToExtract));
 					// Apply the other move actions:

ICSharpCode.Decompiler/IL/Transforms/NamedArgumentTransform.cs

@@ -1,8 +1,5 @@
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
+using System.Diagnostics;
 using System.Linq;
-using System.Text;
 
 using ICSharpCode.Decompiler.TypeSystem;
 
@@ -90,7 +87,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		{
 			var call = (CallInstruction)arg.Parent;
 			Debug.Assert(context.Function == call.Ancestors.OfType<ILFunction>().First());
-			var v = context.Function.RegisterVariable(VariableKind.NamedArgument, arg.ResultType);
+			var type = context.TypeSystem.FindType(arg.ResultType.ToKnownTypeCode());
+			var v = context.Function.RegisterVariable(VariableKind.NamedArgument, type);
 			context.Step($"Introduce named argument '{v.Name}'", arg);
 			if (!(call.Parent is Block namedArgBlock) || namedArgBlock.Kind != BlockKind.CallWithNamedArgs)
 			{

ICSharpCode.Decompiler/IL/Transforms/TransformArrayInitializers.cs

@@ -257,7 +257,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				var otherLoadOfV = v.LoadInstructions.FirstOrDefault(l => !(l.Parent is Cpblk));
 				if (otherLoadOfV == null)
 					return false;
-				finalStore = otherLoadOfV.Parent.Extract();
+				finalStore = otherLoadOfV.Parent.Extract(context);
 				if (finalStore == null)
 					return false;
 				value = ((StLoc)finalStore.StoreInstructions[0]).Value;