Don't use casts for implicit conversions to bool in conditional contexts.

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -532,6 +532,9 @@ namespace ICSharpCode.Decompiler.CSharp
 		
 		internal ExpressionWithResolveResult LogicNot(TranslatedExpression expr)
 		{
+			// "!expr" implicitly converts to bool so we can remove the cast;
+			// but only if doing so wouldn't cause us to call a user-defined "operator !"
+			expr = expr.UnwrapImplicitBoolConversion(type => !type.GetMethods(m => m.IsOperator && m.Name == "op_LogicalNot").Any());
 			return new UnaryOperatorExpression(UnaryOperatorType.Not, expr.Expression)
 				.WithRR(new OperatorResolveResult(compilation.FindType(KnownTypeCode.Boolean), ExpressionType.Not, expr.ResolveResult));
 		}
@@ -2476,6 +2479,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					.WithRR(new ResolveResult(compilation.FindType(KnownTypeCode.Boolean)));
 			}
 
+			condition = condition.UnwrapImplicitBoolConversion();
 			trueBranch = AdjustConstantExpressionToType(trueBranch, falseBranch.Type);
 			falseBranch = AdjustConstantExpressionToType(falseBranch, trueBranch.Type);
 
@@ -2522,7 +2526,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					.WithRR(rr);
 			}
 		}
-		
+
 		protected internal override TranslatedExpression VisitAddressOf(AddressOf inst, TranslationContext context)
 		{
 			IType targetTypeHint = null;

ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

@@ -431,7 +431,27 @@ namespace ICSharpCode.Decompiler.CSharp
 				.WithoutILInstruction()
 				.WithRR(new ConstantResolveResult(compilation.FindType(KnownTypeCode.Int32), val));
 		}
-		
+
+		/// <summary>
+		/// In conditional contexts, remove the bool-cast emitted when converting
+		/// an "implicit operator bool" invocation.
+		/// </summary>
+		public TranslatedExpression UnwrapImplicitBoolConversion(Func<IType, bool> typeFilter = null)
+		{
+			if (!this.Type.IsKnownType(KnownTypeCode.Boolean))
+				return this;
+			if (!(this.ResolveResult is ConversionResolveResult rr))
+				return this;
+			if (!(rr.Conversion.IsUserDefined && rr.Conversion.IsImplicit))
+				return this;
+			if (typeFilter != null && !typeFilter(rr.Input.Type))
+				return this;
+			if (this.Expression is CastExpression cast) {
+				return this.UnwrapChild(cast.Expression);
+			}
+			return this;
+		}
+
 		/// <summary>
 		/// Converts this expression to a boolean expression.
 		///