From 4d4869f06ed5b6465549fc323839d96ab165670b Mon Sep 17 00:00:00 2001
From: Sofia Faro <sofia.faro@digitalasset.com>
Date: Thu, 4 Nov 2021 18:44:48 +0000
Subject: [PATCH] interfaces: Improve fixed choice lookup (#11551)

* interfaces: Improve fixed choice lookup

This PR adds a lazy map to match fixed choice names to their
interface, to improve the worst case for choice lookup.

Part of #10810

changelog_begin
changelog_end

* scalafmt

* apply improvements from remy
---
 .../digitalasset/daml/lf/language/Ast.scala    |  7 ++++++-
 .../daml/lf/language/PackageInterface.scala    | 18 +++++++++---------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/Ast.scala b/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/Ast.scala
index d16a6fdaca..5de2edf776 100644
--- a/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/Ast.scala
+++ b/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/Ast.scala
@@ -712,7 +712,12 @@ object Ast {
       observers: E, // Observers of the contract.
       key: Option[GenTemplateKey[E]],
       implements: Map[TypeConName, GenTemplateImplements[E]],
-  )
+  ) {
+    lazy val inheritedChoices: Map[ChoiceName, TypeConName] =
+      implements.flatMap { case (iface, impl) =>
+        impl.inheritedChoices.view.map(chName => (chName, iface))
+      }
+  }
 
   final class GenTemplateCompanion[E] private[Ast] {
 
diff --git a/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/PackageInterface.scala b/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/PackageInterface.scala
index a1bd9d38ca..0fb1dbf503 100644
--- a/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/PackageInterface.scala
+++ b/daml-lf/language/src/main/scala/com/digitalasset/daml/lf/language/PackageInterface.scala
@@ -6,7 +6,6 @@ package language
 
 import com.daml.lf.data.Ref._
 import com.daml.lf.language.Ast._
-import scalaz._, std.list._, std.either._, syntax.traverse._
 
 private[lf] class PackageInterface(signatures: PartialFunction[PackageId, PackageSignature]) {
 
@@ -202,14 +201,15 @@ private[lf] class PackageInterface(signatures: PartialFunction[PackageId, Packag
       template.choices.get(chName) match {
         case Some(choice) => Right(choice)
         case None =>
-          // TODO https://github.com/digital-asset/daml/issues/10810
-          //  Improve lookup for fixed choices
-          for {
-            ifaces <- template.implements.keys.toList.traverse(lookupInterface(_, context))
-            choices = ifaces.flatMap(_.fixedChoices.get(chName).toList)
-            choice <-
-              choices.headOption.toRight(LookupError(Reference.Choice(tmpName, chName), context))
-          } yield choice
+          template.inheritedChoices.get(chName) match {
+            case None => Left(LookupError(Reference.Choice(tmpName, chName), context))
+            case Some(ifaceName) =>
+              lookupInterface(ifaceName, context).flatMap(iface =>
+                iface.fixedChoices
+                  .get(chName)
+                  .toRight(LookupError(Reference.Choice(ifaceName, chName), context))
+              )
+          }
       }
     )