From e5d9aee00b0c775df1d8e2d8819aeb80dffa73c2 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 1 Mar 2019 17:28:19 +0100
Subject: Split abnf_to_pest and dhall into their own crates

---
 dhall/src/errors/UnboundVariable.txt | 97 ++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 dhall/src/errors/UnboundVariable.txt

(limited to 'dhall/src/errors/UnboundVariable.txt')

diff --git a/dhall/src/errors/UnboundVariable.txt b/dhall/src/errors/UnboundVariable.txt
new file mode 100644
index 0000000..bd7d483
--- /dev/null
+++ b/dhall/src/errors/UnboundVariable.txt
@@ -0,0 +1,97 @@
+Explanation: Expressions can only reference previously introduced (i.e. "bound")
+variables that are still "in scope"
+
+For example, the following valid expressions introduce a "bound" variable named
+❰x❱:
+
+
+    ┌─────────────────┐
+    │ λ(x : Bool) → x │  Anonymous functions introduce "bound" variables
+    └─────────────────┘
+        ⇧
+        This is the bound variable
+
+
+    ┌─────────────────┐
+    │ let x = 1 in x  │  ❰let❱ expressions introduce "bound" variables
+    └─────────────────┘
+          ⇧
+          This is the bound variable
+
+
+However, the following expressions are not valid because they all reference a
+variable that has not been introduced yet (i.e. an "unbound" variable):
+
+
+    ┌─────────────────┐
+    │ λ(x : Bool) → y │  The variable ❰y❱ hasn't been introduced yet
+    └─────────────────┘
+                    ⇧
+                    This is the unbound variable
+
+
+    ┌──────────────────────────┐
+    │ (let x = True in x) && x │  ❰x❱ is undefined outside the parentheses
+    └──────────────────────────┘
+                             ⇧
+                             This is the unbound variable
+
+
+    ┌────────────────┐
+    │ let x = x in x │  The definition for ❰x❱ cannot reference itself
+    └────────────────┘
+              ⇧
+              This is the unbound variable
+
+
+Some common reasons why you might get this error:
+
+● You misspell a variable name, like this:
+
+
+    ┌────────────────────────────────────────────────────┐
+    │ λ(empty : Bool) → if emty then "Empty" else "Full" │
+    └────────────────────────────────────────────────────┘
+                           ⇧
+                           Typo
+
+
+● You misspell a reserved identifier, like this:
+
+
+    ┌──────────────────────────┐
+    │ foral (a : Type) → a → a │
+    └──────────────────────────┘
+      ⇧
+      Typo
+
+
+● You tried to define a recursive value, like this:
+
+
+    ┌─────────────────────┐
+    │ let x = x + +1 in x │
+    └─────────────────────┘
+              ⇧
+              Recursive definitions are not allowed
+
+
+● You accidentally forgot a ❰λ❱ or ❰∀❱/❰forall❱
+
+
+        Unbound variable
+        ⇩
+    ┌─────────────────┐
+    │  (x : Bool) → x │
+    └─────────────────┘
+      ⇧
+      A ❰λ❱ here would transform this into a valid anonymous function 
+
+
+        Unbound variable
+        ⇩
+    ┌────────────────────┐
+    │  (x : Bool) → Bool │
+    └────────────────────┘
+      ⇧
+      A ❰∀❱ or ❰forall❱ here would transform this into a valid function type
-- 
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