Fix #22300 Document GHC's extensions to valid whitespace

2 files changed, 30 insertions, 0 deletions

diff --git a/docs/users_guide/exts/misc.rst b/docs/users_guide/exts/misc.rst
index 7e51ffe80a..b5d7f78a86 100644
--- a/docs/users_guide/exts/misc.rst
+++ b/docs/users_guide/exts/misc.rst
@@ -9,3 +9,4 @@ Miscellaneous
     generics
     assert
     callstack
+    whitespace
diff --git a/docs/users_guide/exts/whitespace.rst b/docs/users_guide/exts/whitespace.rst
new file mode 100644
index 0000000000..6defc2b4e0
--- /dev/null
+++ b/docs/users_guide/exts/whitespace.rst
@@ -0,0 +1,29 @@
+.. _whitespace:
+
+Whitespace
+==========
+
+.. index::
+   single: Whitespace
+
+As in the Haskell Language Report, Haskell comments are valid whitespace. In
+addition, lines (which must end with a line feed character) that begin as
+follows are valid whitespace in source code, except immediately after a
+``where``, ``let``, ``do`` or ``of`` keyword:
+
+-  ``#!``. This accommodates 'shebang' interpreter directives in scripts on
+   Unix-like operating systems.
+
+-  ``<space>#!``, where ``<space>`` is an initial space character before the
+   'shebang'.
+
+-  ``#pragma``. This accommodates the use of a directive that passes additional
+   information to a compiler.
+
+-  ``#line <line> "<file>"``, where ``<line>`` is a positive integer and
+   ``<file>`` can comprise zero or more characters. This accommodates a compiler
+   directive that resets the numbering of lines of source code, and the
+   identification of the source code file name, in compiler messages.
+
+-  ``#<line> "<file>"``, where ``<line>`` is a positive integer and ``<file>``
+   can comprise zero or more characters.