Better errors related to Interface Views (#14648)

* Point to new GHC with errors for missing views

* Add placeholder view to ImplementsNonInterface

* Fix doc comment in InterfaceViewNotSpecified

* Add test for error when method named `view` is declared

* Add placeholder unit viewtype to doc tests

* Update err message in ImplementsNonInterface - error now detected in LF

* empty changelog commit

CHANGELOG_BEGIN
CHANGELOG_END

bazel_tools/ghc-lib/version.bzl

@@ -9,7 +9,7 @@ GHC_LIB_PATCHES = [
 ]
 
 GHC_REPO_URL = "https://github.com/digital-asset/ghc"
-GHC_REV = "0bb070fac5370b2a68d5e132b4c74a36cbaf4d29"
+GHC_REV = "3af876d60209705afc0acac5e196a44f570e6e72"
 GHC_PATCHES = [
 ]
 

compiler/damlc/daml-doc/test/DA/Daml/Doc/Tests.hs

@@ -187,13 +187,16 @@ unitTests =
            Nothing
            "Interface implementations"
            [ testModHdr
+           , "data EmptyInterfaceView = EmptyInterfaceView"
            , "interface Bar where"
+           , "  viewtype EmptyInterfaceView"
            , "  method : Update ()"
            , "template Foo with"
            , "    field1 : Party"
            , "  where"
            , "    signatory field1"
            , "    implements Bar where"
+           , "      view = EmptyInterfaceView"
            , "      method = pure ()"
            ]
            (\md -> assertBool

compiler/damlc/tests/daml-test-files/ImplementsNonInterface.daml

@@ -6,7 +6,7 @@
 -- is caught prior due to missing Eq and Show instances.
 
 -- @SINCE-LF-FEATURE DAML_INTERFACE
--- @ERROR range=18:5-18:20; Invalid 'interface instance Bool for T': 'Bool' is not an interface
+-- @ERROR range=19:7-19:16; No instance for (HasInterfaceTypeRep Bool)
 
 module ImplementsNonInterface where
 
@@ -15,4 +15,5 @@ template T
     p : Party
   where
     signatory p
-    implements Bool
+    implements Bool where
+      view = ()

compiler/damlc/tests/daml-test-files/InterfaceMethodNamedView.daml

@@ -0,0 +1,13 @@
+-- Copyright (c) 2022 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+-- SPDX-License-Identifier: Apache-2.0
+
+-- @SINCE-LF-FEATURE DAML_INTERFACE
+-- @ERROR range=13:3-13:7; Interface methods with name `view` are disallowed.
+
+-- | Check that error is thrown if method with name `view` is declared
+module InterfaceMethodNamedView where
+
+data UnitPlaceholderView = UnitPlaceholderView
+
+interface I where
+  view : UnitPlaceholderView

compiler/damlc/tests/daml-test-files/InterfaceViewNotSpecified.daml

@@ -4,7 +4,7 @@
 -- @SINCE-LF-FEATURE DAML_INTERFACE
 -- @ERROR range=10:11-10:12; No view found for interface I
 
--- | Check that no error is thrown if interface view exists and is serializable
+-- | Check that error is thrown if no view is specified
 module InterfaceViewNotSpecified where
 
 interface I where