From 4f1892b0c85c3dc586f179ca7e3a689cdd9dfdc7 Mon Sep 17 00:00:00 2001
From: Remy <remy.haemmerle@daml.com>
Date: Wed, 8 Dec 2021 14:34:39 +0100
Subject: [PATCH] Speedy: Implement EToRequiredInterface and
 EFromRequiredInterface (#12046)

Part of #11978.

CHANGELOG_BEGIN
CHANGELOG_END
---
 .../daml/lf/speedy/Compiler.scala             |  8 +++----
 .../daml/lf/speedy/SBuiltin.scala             | 22 +++++++++++++++++++
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala b/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala
index d43a734ce8c1..0941a00f2ba8 100644
--- a/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala
+++ b/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala
@@ -578,11 +578,9 @@ private[lf] final class Compiler(
       case ECallInterface(iface, methodName, e) =>
         SBCallInterface(iface, methodName)(compile(env, e))
       case EToRequiredInterface(requiredIfaceId @ _, requiringIfaceId @ _, body @ _) =>
-        // TODO https://github.com/digital-asset/daml/issues/11978
-        throw CompilationError("EToRequiredInterface is not implemented")
-      case EFromRequiredInterface(requiredIfaceId @ _, requiringIfaceId @ _, body @ _) =>
-        // TODO https://github.com/digital-asset/daml/issues/11978
-        throw CompilationError("EFromRequiredInterface is not implemented")
+        compile(env, body)
+      case EFromRequiredInterface(requiredIfaceId @ _, requiringIfaceId, body @ _) =>
+        SBFromRequiredInterface(requiringIfaceId)(compile(env, body))
       case EExperimental(name, _) =>
         SBExperimental(name)
 
diff --git a/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala b/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala
index e1cab2ee8920..5b2227fd2df6 100644
--- a/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala
+++ b/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala
@@ -1251,6 +1251,28 @@ private[lf] object SBuiltin {
     }
   }
 
+  // Convert an interface `requiredIface` to another interface `requiringIface`, if
+  // the `requiringIface` implements `requiredIface`.
+  final case class SBFromRequiredInterface(
+      requiringIface: TypeConName
+  ) extends SBuiltin(1) {
+
+    override private[speedy] def execute(
+        args: util.ArrayList[SValue],
+        machine: Machine,
+    ) = {
+      val record = getSRecord(args, 0)
+      // TODO https://github.com/digital-asset/daml/issues/11345
+      //  The lookup is probably slow. We may want to investigate way to make the feature faster.
+      machine.returnValue = machine.compiledPackages.interface.lookupTemplate(record.id) match {
+        case Right(ifaceSignature) if ifaceSignature.implements.contains(requiringIface) =>
+          SOptional(Some(record))
+        case _ =>
+          SOptional(None)
+      }
+    }
+  }
+
   final case class SBCallInterface(
       ifaceId: TypeConName,
       methodName: MethodName,