Added grammar support to enum defaults

Author: RobertoRoos

src/plcdoc/st_declaration.tx

@@ -67,6 +67,7 @@ TypeEnum:
     CommentAny*
     ')'
     (base_type=Fqn)?
+    (default=EnumDefault)?
     ';'
 ;
 
@@ -78,6 +79,12 @@ EnumOption:
     (comment=CommentLine)?
 ;
 
+EnumDefault:
+   ':='
+   option=ID
+   // Enum default must be a literal field, it cannot be e.g. an integer
+;
+
 TypeAlias:
    base=VariableType
    CommentAny*

tests/plc_code/E_Filter.txt

@@ -14,3 +14,11 @@ TYPE E_Filter :
     Filter697nm := 6    // Note: non-consecutive number!
 ) USINT;                // Specify base type so API is explicit
 END_TYPE
+
+TYPE E_FilterDefault :
+(
+    NoFilter := 0,
+    Filter434nm,
+    Filter697nm
+) USINT := NoFilter;
+END_TYPE

tests/plc_code/E_Options.txt

@@ -1,7 +1,15 @@
 TYPE E_Options :
 (
-	Default := 0,
+	 Default := 0,
     Option1,
     Option2
 );
 END_TYPE
+
+TYPE E_OptionsDefault :
+(
+	 Default := 0,
+    Option1,
+    Option2
+) := DEFAULT;
+END_TYPE