Make IParserAdapter implement ICompilable to support compilation

Co-authored-by: sebastienros <1165805+sebastienros@users.noreply.github.com>

src/Parlot/Fluent/IParserAdapter.cs

@@ -1,12 +1,14 @@
+using Parlot.Compilation;
 using Parlot.Rewriting;
+using System.Linq.Expressions;
 
 namespace Parlot.Fluent;
 
 /// <summary>
 /// Adapts an IParser&lt;T&gt; to a Parser&lt;T&gt; for use in contexts that require Parser.
 /// This is used internally to support covariance.
 /// </summary>
-internal sealed class IParserAdapter<T> : Parser<T>, ISeekable
+internal sealed class IParserAdapter<T> : Parser<T>, ISeekable, ICompilable
 {
     private readonly IParser<T> _parser;
 
@@ -39,5 +41,47 @@ public override bool Parse(ParseContext context, ref ParseResult<T> result)
         return success;
     }
 
+    public CompilationResult Compile(CompilationContext context)
+    {
+        // If the wrapped parser is actually a Parser<T>, delegate compilation to it
+        if (_parser is Parser<T> parser)
+        {
+            return parser.Build(context);
+        }
+
+        // Otherwise, fall back to the default non-compilable behavior
+        // This uses the Parse method which will work with any IParser<T>
+        var result = context.CreateCompilationResult<T>(false);
+
+        // ParseResult<T> parseResult;
+        var parseResult = Expression.Variable(typeof(ParseResult<T>), $"value{context.NextNumber}");
+        result.Variables.Add(parseResult);
+
+        // success = this.Parse(context.ParseContext, ref parseResult)
+        result.Body.Add(
+            Expression.Assign(result.Success,
+                Expression.Call(
+                    Expression.Constant(this),
+                    GetType().GetMethod("Parse", [typeof(ParseContext), typeof(ParseResult<T>).MakeByRefType()])!,
+                    context.ParseContext,
+                    parseResult))
+            );
+
+        if (!context.DiscardResult)
+        {
+            var value = result.Value = Expression.Variable(typeof(T), $"value{context.NextNumber}");
+            result.Variables.Add(value);
+
+            result.Body.Add(
+                Expression.IfThen(
+                    result.Success,
+                    Expression.Assign(value, Expression.Field(parseResult, "Value"))
+                    )
+                );
+        }
+
+        return result;
+    }
+
     public override string ToString() => _parser.ToString() ?? "IParserAdapter";
 }