Add NoFieldSelectors example to GHC-88464

Author: tbidne

message-index/messages/GHC-88464/example3/after/A.hs

@@ -0,0 +1,5 @@
+{-# LANGUAGE NoFieldSelectors #-}
+
+module A (Foo (..)) where
+
+data Foo = MkFoo { fint :: Int, fchar :: Char }

message-index/messages/GHC-88464/example3/after/Example3.hs

@@ -0,0 +1,18 @@
+module Example3 where
+
+import A (Foo (MkFoo, fint, fchar))
+
+getFooInt :: Foo -> Int
+getFooInt (MkFoo i _) = i -- this is fine
+
+-- Creation and updates below are fine
+
+mkFoo :: Foo
+mkFoo =
+  MkFoo
+    { fint = 0,
+      fchar = 'a'
+    }
+
+setFooInt :: Foo -> Int -> Foo
+setFooInt f x = f { fint = x }

message-index/messages/GHC-88464/example3/before/A.hs

@@ -0,0 +1,5 @@
+{-# LANGUAGE NoFieldSelectors #-}
+
+module A (Foo (..)) where
+
+data Foo = MkFoo { fint :: Int, fchar :: Char }

message-index/messages/GHC-88464/example3/before/Example3.hs

@@ -0,0 +1,18 @@
+module Example3 where
+
+import A (Foo (MkFoo, fint, fchar))
+
+getFooInt :: Foo -> Int
+getFooInt = fint -- this is the problem
+
+-- Creation and updates below are fine
+
+mkFoo :: Foo
+mkFoo =
+  MkFoo
+    { fint = 0,
+      fchar = 'a'
+    }
+
+setFooInt :: Foo -> Int -> Foo
+setFooInt f x = f { fint = x }

message-index/messages/GHC-88464/example3/index.md

@@ -0,0 +1,22 @@
+---
+title: Attempted to use a field selector disabled with NoFieldSelectors
+---
+
+## Error Message
+
+```
+Example3.hs:14:13: error: [GHC-88464]
+    Variable not in scope: fint :: Foo -> Int
+    Suggested fix:
+      Notice that ‘fint’ is a field selector belonging to the type ‘Foo’
+      that has been suppressed by NoFieldSelectors.
+   |
+14 | getFooInt = fint
+   |             ^^^^
+```
+
+## Description
+
+This example attempts to use the field selector `fint`, despite it being disabled at the definition site (`A.hs`) with `NoFieldSelectors`. This fix is to use pattern matching instead.
+
+Notice that record creation and updates still work with `NoFieldSelectors`.