Translate the initializer of a `fixed` statement as managed reference and only apply the ref-to-pointer conversion at the end.

This way we create compilable code when the pinned variable type does not match the initializer type.

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

@@ -1,5 +1,6 @@
 using System;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 
 [assembly: AssemblyFileVersion("4.0.0.0")]
 [assembly: AssemblyInformationalVersion("4.0.0.0")]
@@ -12,6 +13,15 @@ using System.Reflection;
 [assembly: AssemblyProduct("Microsoft® .NET Framework")]
 [assembly: CLSCompliant(false)]
 
+internal sealed class ExtraUnsafeTests
+{
+	public unsafe static void PinWithTypeMismatch(ref uint managedPtr)
+	{
+		fixed (ushort* ptr = &Unsafe.As<uint, ushort>(ref managedPtr)) {
+		}
+	}
+}
+
 namespace System.Runtime.CompilerServices
 {
 	public static class Unsafe

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

@@ -437,3 +437,33 @@
 
 } // end of class System.Runtime.CompilerServices.IsReadOnlyAttribute
 #endif
+
+.class private auto ansi sealed beforefieldinit ExtraUnsafeTests
+  extends [CORE_ASSEMBLY]System.Object
+{
+  .method public hidebysig specialname rtspecialname 
+          instance void .ctor () cil managed 
+  {
+        .maxstack 1
+        ldarg.0
+        call instance void [CORE_ASSEMBLY]System.Object::.ctor()
+        ret
+  } // end of method ExtraUnsafeTests::.ctor
+
+  .method public hidebysig static void PinWithTypeMismatch(uint32& managedPtr)
+  {
+    .maxstack 8
+    .locals (
+      [0] uint16& pinned
+    )
+    // Pin:
+    ldarg.0
+    stloc.0
+
+    // Unpin:
+    ldc.i4 0
+    stloc.0
+
+    ret
+  }
+}

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -832,7 +832,19 @@ namespace ICSharpCode.Decompiler.CSharp
 					initExpr = exprBuilder.Translate(gpr.Argument);
 				}
 			} else {
-				initExpr = exprBuilder.Translate(inst.Init, typeHint: inst.Variable.Type).ConvertTo(inst.Variable.Type, exprBuilder);
+				IType refType = inst.Variable.Type;
+				if (refType is PointerType pointerType) {
+					refType = new ByReferenceType(pointerType.ElementType);
+				}
+				initExpr = exprBuilder.Translate(inst.Init, typeHint: refType).ConvertTo(refType, exprBuilder);
+				if (initExpr is DirectionExpression dirExpr) {
+					if (dirExpr.Expression is UnaryOperatorExpression uoe && uoe.Operator == UnaryOperatorType.Dereference) {
+						initExpr = uoe.Expression.Detach();
+					} else {
+						initExpr = new UnaryOperatorExpression(UnaryOperatorType.AddressOf, dirExpr.Expression.Detach())
+							.WithRR(new ResolveResult(inst.Variable.Type));
+					}
+				}
 			}
 			fixedStmt.Variables.Add(new VariableInitializer(inst.Variable.Name, initExpr).WithILVariable(inst.Variable));
 			fixedStmt.EmbeddedStatement = Convert(inst.Body);