Use type analysis to introduce casts to float/double only where required.

ICSharpCode.Decompiler/Ast/AstMethodBodyBuilder.cs

@@ -377,9 +377,10 @@ namespace ICSharpCode.Decompiler.Ast
 						}
 						return arg1;
 					}
-					case ILCode.Conv_R4:   return arg1.CastTo(typeof(float));
-					case ILCode.Conv_R8:   return arg1.CastTo(typeof(double));
-					case ILCode.Conv_R_Un: return arg1.CastTo(typeof(double)); // TODO
+				case ILCode.Conv_R4:
+				case ILCode.Conv_R8:
+				case ILCode.Conv_R_Un: // TODO
+					return arg1;
 				case ILCode.Conv_Ovf_I1:
 				case ILCode.Conv_Ovf_I2:
 				case ILCode.Conv_Ovf_I4:
@@ -908,8 +909,10 @@ namespace ICSharpCode.Decompiler.Ast
 				{
 					return expr.CastTo(AstBuilder.ConvertType(actualType));
 				}
-
-				if (actualIsIntegerOrEnum && requiredIsIntegerOrEnum) {
+				
+				bool actualIsPrimitiveType = actualIsIntegerOrEnum || actualType.MetadataType == MetadataType.Single || actualType.MetadataType == MetadataType.Double;
+				bool requiredIsPrimitiveType = requiredIsIntegerOrEnum || reqType.MetadataType == MetadataType.Single || reqType.MetadataType == MetadataType.Double;
+				if (actualIsPrimitiveType && requiredIsPrimitiveType) {
 					if (actualType.FullName == reqType.FullName)
 						return expr;
 					return expr.CastTo(AstBuilder.ConvertType(reqType));

ICSharpCode.Decompiler/ILAst/TypeAnalysis.cs

@@ -604,8 +604,14 @@ namespace ICSharpCode.Decompiler.ILAst
 				case ILCode.Conv_Ovf_U_Un:
 					return HandleConversion(NativeInt, false, expr.Arguments[0], expectedType, typeSystem.UIntPtr);
 				case ILCode.Conv_R4:
+					if (forceInferChildren) {
+						InferTypeForExpression(expr.Arguments[0], typeSystem.Single);
+					}
 					return typeSystem.Single;
 				case ILCode.Conv_R8:
+					if (forceInferChildren) {
+						InferTypeForExpression(expr.Arguments[0], typeSystem.Double);
+					}
 					return typeSystem.Double;
 				case ILCode.Conv_R_Un:
 					return (expectedType != null  && expectedType.MetadataType == MetadataType.Single) ? typeSystem.Single : typeSystem.Double;