From 60129b7d1c0ea8bdf2ec666fa51957e97465e88f Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 6 May 2019 23:17:26 +0200
Subject: Consolidate errors in the error module

---
 dhall/src/error/text/UnusedHandler.txt | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 dhall/src/error/text/UnusedHandler.txt

(limited to 'dhall/src/error/text/UnusedHandler.txt')

diff --git a/dhall/src/error/text/UnusedHandler.txt b/dhall/src/error/text/UnusedHandler.txt
new file mode 100644
index 0000000..2e46a12
--- /dev/null
+++ b/dhall/src/error/text/UnusedHandler.txt
@@ -0,0 +1,32 @@
+Explanation: You can ❰merge❱ the alternatives of a union using a record with one
+handler per alternative, like this:
+
+
+    ┌─────────────────────────────────────────────────────────────────────┐
+    │     let union    = < Left = +2 | Right : Bool >                     │
+    │ in  let handlers = { Left = Natural/even, Right = λ(x : Bool) → x } │
+    │ in  merge handlers union : Bool                                     │
+    └─────────────────────────────────────────────────────────────────────┘
+
+
+... but you must provide exactly one handler per alternative in the union.  You
+cannot supply extra handlers
+
+For example, the following expression is $_NOT valid:
+
+
+    ┌───────────────────────────────────────┐
+    │     let union    = < Left = +2 >      │  The ❰Right❱ alternative is missing
+    │ in  let handlers =                    │ 
+    │             { Left  = Natural/even    │
+    │             , Right = λ(x : Bool) → x │  Invalid: ❰Right❱ handler isn't used
+    │             }                         │
+    │ in  merge handlers union : Bool       │
+    └───────────────────────────────────────┘
+
+
+You provided the following handlers:
+
+↳ $txt0
+
+... which had no matching alternatives in the union you tried to ❰merge❱
-- 
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