From 474b477deb75ba161d4e29a7b0e20dba7e0563a4 Mon Sep 17 00:00:00 2001
From: Ivan Bondarev <ibond84@googlemail.com>
Date: Tue, 16 Mar 2021 20:29:26 +0100
Subject: [PATCH] #2092

---
 TestSuite/generics51.pas                  | 17 +++++++++++++
 TreeConverter/TreeRealization/generics.cs | 30 ++++++++++++++++++++---
 2 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 TestSuite/generics51.pas

diff --git a/TestSuite/generics51.pas b/TestSuite/generics51.pas
new file mode 100644
index 000000000..0d819bf20
--- /dev/null
+++ b/TestSuite/generics51.pas
@@ -0,0 +1,17 @@
+type
+  I1<T>=interface end;
+  C1<T>=class(I1<T>) end;
+  C2=class(C1<integer>) end;
+
+procedure p1<T,T1>(self: sequence of T; l: T->T1; o: I1<T1>); extensionmethod;
+begin
+  assert(typeof(T) = typeof(byte));
+  assert(typeof(T1) = typeof(integer));
+end;
+procedure p2<T,T1>(self: sequence of T; o: I1<T1>); extensionmethod := exit;
+
+begin
+  // любая 1 из этих строк даёт ошибку:
+  Seq&<byte>.p1(b->0,new C2);
+  Seq&<byte>.p2(new C2);
+end.
\ No newline at end of file
diff --git a/TreeConverter/TreeRealization/generics.cs b/TreeConverter/TreeRealization/generics.cs
index 001116943..435bcf712 100644
--- a/TreeConverter/TreeRealization/generics.cs
+++ b/TreeConverter/TreeRealization/generics.cs
@@ -1282,14 +1282,36 @@ namespace PascalABCCompiler.TreeRealization
                         base_type = base_type.base_type;
                     }
                     if (fact_type.ImplementingInterfaces != null && fact_type_converted == null)
-                    foreach (type_node ti in fact_type.ImplementingInterfaces)
                     {
-                        if (ti.original_generic == formal_type.original_generic)
+                        foreach (type_node ti in fact_type.ImplementingInterfaces)
                         {
-                            fact_type_converted = ti;
-                            break;
+                            if (ti.original_generic == formal_type.original_generic)
+                            {
+                                fact_type_converted = ti;
+                                break;
+                            }
+                        }
+                        if (fact_type_converted == null)
+                        {
+                            base_type = fact_type.base_type;
+                            while (base_type != null)
+                            {
+                                if (base_type.ImplementingInterfaces != null)
+                                foreach (type_node ti in base_type.ImplementingInterfaces)
+                                {
+                                    if (ti.original_generic == formal_type.original_generic)
+                                    {
+                                        fact_type_converted = ti;
+                                        break;
+                                    }
+                                }
+                                if (fact_type_converted != null)
+                                    break;
+                                base_type = base_type.base_type;
+                            }
                         }
                     }
+                    
                     if (fact_type_converted == null) goto eq_cmp;
                 }
                 else