Issue#1503: Added docs for rule to check that signal assignment operator is not a different line than preceding tokens.

Author: JHertz5

docs/rule_groups/structure_rule_group.rst

@@ -173,6 +173,7 @@ Rules Enforcing Structure Rule Group
 * `signal_007 <../signal_rules.html#signal-007>`_
 * `signal_015 <../signal_rules.html#signal-015>`_
 * `signal_017 <../signal_rules.html#signal-017>`_
+* `signal_018 <../signal_rules.html#signal-018>`_
 * `source_file_001 <../source_file_rules.html#source-file-001>`_
 * `subprogram_instantiation_001 <../subprogram_instantiation_rules.html#subprogram-instantiation-001>`_
 * `subprogram_instantiation_002 <../subprogram_instantiation_rules.html#subprogram-instantiation-002>`_

docs/signal_rules.rst

@@ -334,6 +334,31 @@ This rule checks the structure of signal constraints.
        element2(3 downto 0)
      );
 
+signal_018
+##########
+
+|phase_1| |error| |structure|
+
+This rule checks the **:=** is on the same line at the **signal** keyword.
+
+**Violation**
+
+.. code-block:: vhdl
+
+   signal size : integer
+      := 1;
+   signal width : integer
+      := 32;
+
+**Fix**
+
+.. code-block:: vhdl
+
+   signal size    : integer :=
+     1;
+   signal width   : integer :=
+     32
+
 signal_100
 ##########