Improve TypeBuilderInstantiation error messages to guide users to TypeBuilder static methods (#118638)

Fixes #118506

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Author: Copilot

src/libraries/System.Private.CoreLib/src/Resources/Strings.resx

@@ -3014,6 +3014,9 @@
   <data name="NotSupported_CreateInstanceWithTypeBuilder" xml:space="preserve">
     <value>CreateInstance cannot be used with an object of type TypeBuilder.</value>
   </data>
+  <data name="NotSupported_TypeBuilderInstantiation_ResolvingMembers" xml:space="preserve">
+    <value>TypeBuilder generic instantiation does not support resolving members. Use TypeBuilder.{0} instead.</value>
+  </data>
   <data name="NotSupported_DBNullSerial" xml:space="preserve">
     <value>Only one DBNull instance may exist, and calls to DBNull deserialization methods are not allowed.</value>
   </data>

src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilderInstantiation.cs

@@ -161,22 +161,22 @@ public override Type? BaseType
             }
         }
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
-        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder? binder, CallingConventions callConvention, Type[] types, ParameterModifier[]? modifiers) { throw new NotSupportedException(); }
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder? binder, CallingConventions callConvention, Type[] types, ParameterModifier[]? modifiers) { throw new NotSupportedException(SR.Format(SR.NotSupported_TypeBuilderInstantiation_ResolvingMembers, nameof(TypeBuilder.GetConstructor))); }
 
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
-        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr) { throw new NotSupportedException(SR.Format(SR.NotSupported_TypeBuilderInstantiation_ResolvingMembers, nameof(TypeBuilder.GetConstructor))); }
 
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)]
-        protected override MethodInfo GetMethodImpl(string name, BindingFlags bindingAttr, Binder? binder, CallingConventions callConvention, Type[]? types, ParameterModifier[]? modifiers) { throw new NotSupportedException(); }
+        protected override MethodInfo GetMethodImpl(string name, BindingFlags bindingAttr, Binder? binder, CallingConventions callConvention, Type[]? types, ParameterModifier[]? modifiers) { throw new NotSupportedException(SR.Format(SR.NotSupported_TypeBuilderInstantiation_ResolvingMembers, nameof(TypeBuilder.GetMethod))); }
 
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)]
-        public override MethodInfo[] GetMethods(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr) { throw new NotSupportedException(SR.Format(SR.NotSupported_TypeBuilderInstantiation_ResolvingMembers, nameof(TypeBuilder.GetMethod))); }
 
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields | DynamicallyAccessedMemberTypes.NonPublicFields)]
-        public override FieldInfo GetField(string name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override FieldInfo GetField(string name, BindingFlags bindingAttr) { throw new NotSupportedException(SR.Format(SR.NotSupported_TypeBuilderInstantiation_ResolvingMembers, nameof(TypeBuilder.GetField))); }
 
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields | DynamicallyAccessedMemberTypes.NonPublicFields)]
-        public override FieldInfo[] GetFields(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr) { throw new NotSupportedException(SR.Format(SR.NotSupported_TypeBuilderInstantiation_ResolvingMembers, nameof(TypeBuilder.GetField))); }
 
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.Interfaces)]
         [return: DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.Interfaces)]

src/libraries/System.Reflection.Emit/tests/TypeBuilder/TypeBuilderInstantiationErrorMessageTests.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace System.Reflection.Emit.Tests
+{
+    public class TypeBuilderInstantiationErrorMessageTests
+    {
+        [Fact]
+        public void TypeBuilderInstantiation_ThrowsWithHelpfulMessage()
+        {
+            TypeBuilder type = Helpers.DynamicType(TypeAttributes.Public);
+
+            type.DefineGenericParameters("T");
+            
+            Type instantiatedType = type.MakeGenericType(typeof(string));
+
+            AssertThrowsWithHelpfulMessage(nameof(TypeBuilder.GetConstructor), () => instantiatedType.GetConstructor(Type.EmptyTypes));
+            AssertThrowsWithHelpfulMessage(nameof(TypeBuilder.GetConstructor), () => instantiatedType.GetConstructors());
+            AssertThrowsWithHelpfulMessage(nameof(TypeBuilder.GetMethod), () => instantiatedType.GetMethod("Test"));
+            AssertThrowsWithHelpfulMessage(nameof(TypeBuilder.GetMethod), () => instantiatedType.GetMethods());
+            AssertThrowsWithHelpfulMessage(nameof(TypeBuilder.GetField), () => instantiatedType.GetField("_test"));
+            AssertThrowsWithHelpfulMessage(nameof(TypeBuilder.GetField), () => instantiatedType.GetFields());
+
+            static void AssertThrowsWithHelpfulMessage(string suggestedAlternative, TestDelegate code)
+            {
+                 NotSupportedException ex = Assert.Throws<NotSupportedException>(code);
+                 Assert.Contains($"TypeBuilder.{suggestedAlternative}", ex.Message);
+            }
+        }
+}