@wip added test for #476

Author: Maksim Volkau

src/FastExpressionCompiler/FastExpressionCompiler.cs

@@ -5055,8 +5055,8 @@ public static bool TryEmitMemberGet(MemberExpression expr,
                             // Value type special treatment to load address of value instance in order to call a method.
                             // For the parameters, we will skip the address loading because the `LastEmitIsAddress == true` for `Ldarga`,
                             // so the condition here will be skipped
-                            if (!closure.LastEmitIsAddress && objExpr.Type.IsValueType)
-                            EmitStoreAndLoadLocalVariableAddress(il, objExpr.Type);
+                            if (!closure.LastEmitIsAddress && !objExpr.Type.IsByRef && objExpr.Type.IsValueType)
+                                EmitStoreAndLoadLocalVariableAddress(il, objExpr.Type);
                     }
 
                     closure.LastEmitIsAddress = false;

test/FastExpressionCompiler.IssueTests/Issue476_System_ExecutionEngineException_with_nullables_on_repeated_calls_to_ConcurrentDictionary copy.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Text.Json;
+
+#if LIGHT_EXPRESSION
+using FastExpressionCompiler.LightExpression.ImTools;
+using static FastExpressionCompiler.LightExpression.Expression;
+namespace FastExpressionCompiler.LightExpression.IssueTests;
+#else
+using System.Linq.Expressions;
+using FastExpressionCompiler.ImTools;
+using static System.Linq.Expressions.Expression;
+namespace FastExpressionCompiler.IssueTests;
+#endif
+
+public struct Issue490_Regression_in_compiling_lambdas_with_ref_struct_parameters : ITestX
+{
+    public void Run(TestRun t)
+    {
+        Original_case(t);
+    }
+
+    private delegate int TestDelegate(ref  Utf8JsonReader reader);
+
+    public void Original_case(TestContext t)
+    {
+        var param = Parameter(typeof(Utf8JsonReader).MakeByRefType());
+        var body = Condition(
+            Equal(Property(param, "TokenType"), Constant(JsonTokenType.Null)),
+            Default(typeof(int)),
+            Call(param, "GetInt32", Type.EmptyTypes)
+        );
+        var expr = Lambda<TestDelegate>(body, param);
+        expr.PrintCSharp();
+
+        var fs = expr.CompileSys();
+        fs.PrintIL();
+
+        // make reader and advance to the Null token
+        var reader = new Utf8JsonReader("null"u8);
+        reader.Read();
+        t.AreEqual(JsonTokenType.Null, reader.TokenType);
+
+        // the compiled function should return default(int), yet it calls reader.GetInt32 instead
+        var a = fs(ref reader);
+        t.AreEqual(default, a);
+
+        var ff = expr.CompileFast(false);
+        ff.PrintIL();
+
+        var b = ff(ref reader);
+        t.AreEqual(default, b);
+    }
+}

test/FastExpressionCompiler.TestsRunner/Program.cs

@@ -27,6 +27,7 @@ public static void Main()
 
             var t = new LightExpression.TestRun(LightExpression.TestFlags.RethrowException);
 
+            t.Run(new LightExpression.IssueTests.Issue490_Regression_in_compiling_lambdas_with_ref_struct_parameters());
             t.Run(new LightExpression.IssueTests.Issue398_Optimize_Switch_with_OpCodes_Switch());
             t.Run(new LightExpression.IssueTests.Issue468_Optimize_the_delegate_access_to_the_Closure_object_for_the_modern_NET());
             t.Run(new LightExpression.IssueTests.Issue472_TryInterpret_and_Reduce_primitive_arithmetic_and_logical_expressions_during_the_compilation());