[spec] Simplify VarDeclarations grammar (#3712)

* [spec] Simplify VarDeclarations grammar

C multiple identifier variable declarations with separate type suffixes
are no longer supported, so *VarDeclarations* no longer needs to use
*Declarators* and the grammar can be simplified.
*Declarator* is kept for uses in other files, but could be inlined.
I've changed the old alias grammar to be more precise using
*Identifiers*, as using a different *TypeSuffix* for a second identifier
is an error anyway. (AIUI each identifier is the same type).

* See also AutoDeclaration

Author: ntrel

spec/declaration.dd

@@ -41,32 +41,26 @@ $(H3 $(LNAME2 variable-declarations, Variable Declarations))
 
 $(GRAMMAR
 $(GNAME VarDeclarations):
-    $(GLINK StorageClasses)$(OPT) $(GLINK2 type, BasicType) $(GLINK Declarators) $(D ;)
+    $(GLINK StorageClasses)$(OPT) $(GLINK2 type, BasicType) $(GLINK2 type, TypeSuffixes)$(OPT) $(GLINK IdentifierInitializers) $(D ;)
     $(GLINK AutoDeclaration)
 
-$(GNAME Declarators):
-    $(GLINK DeclaratorInitializer)
-    $(GLINK DeclaratorInitializer) $(D ,) $(GLINK DeclaratorIdentifierList)
+$(GNAME IdentifierInitializers): $(LEGACY_LNAME2 Declarators, DeclaratorIdentifierList)
+    $(GLINK IdentifierInitializer)
+    $(GLINK IdentifierInitializer) $(D ,) $(GSELF IdentifierInitializers)
 
-$(GNAME DeclaratorInitializer):
-    $(GLINK VarDeclarator)
-    $(GLINK VarDeclarator) $(GLINK2 template, TemplateParameters)$(OPT) $(D =) $(GLINK Initializer)
-
-$(GNAME DeclaratorIdentifierList):
-    $(GLINK DeclaratorIdentifier)
-    $(GLINK DeclaratorIdentifier) $(D ,) $(GSELF DeclaratorIdentifierList)
-
-$(GNAME DeclaratorIdentifier):$(LEGACY_LNAME2 VarDeclaratorIdentifier)
+$(GNAME IdentifierInitializer): $(LEGACY_LNAME2 DeclaratorInitializer, DeclaratorIdentifier)
     $(GLINK_LEX Identifier)
     $(GLINK_LEX Identifier) $(GLINK2 template, TemplateParameters)$(OPT) $(D =) $(GLINK Initializer)
 
-$(GNAME Declarator):
-    $(GLINK VarDeclarator)
-
-$(GNAME VarDeclarator):
+$(GNAME Declarator): $(LEGACY_LNAME2 VarDeclarator)
     $(GLINK2 type, TypeSuffixes)$(OPT) $(GLINK_LEX Identifier)
 )
 
+    $(P See also:)
+    * $(RELATIVE_LINK2 declaration_syntax, Declaration Syntax)
+    * $(GLINK AutoDeclaration)
+    * $(DDSUBLINK spec/template, variable-template, Variable Templates)
+
 $(H3 $(LNAME2 storage-classes, Storage Classes))
 
     $(P See $(RELATIVE_LINK2 typequal_vs_storageclass, Type Classes vs. Storage Classes).)
@@ -233,10 +227,14 @@ $(H2 $(LNAME2 alias, Alias Declarations))
 
 $(GRAMMAR
 $(GNAME AliasDeclaration):
-    $(D alias) $(GLINK StorageClasses)$(OPT) $(GLINK2 type, BasicType) $(GLINK Declarators) $(D ;)
+    $(D alias) $(GLINK StorageClasses)$(OPT) $(GLINK2 type, BasicType) $(GLINK2 type, TypeSuffixes)$(OPT) $(GLINK Identifiers) $(D ;)
     $(D alias) $(GLINK StorageClasses)$(OPT) $(GLINK2 type, BasicType) $(GLINK2 function, FuncDeclarator) $(D ;)
     $(D alias) $(GLINK AliasAssignments) $(D ;)
 
+$(GNAME Identifiers):
+    $(GLINK_LEX Identifier)
+    $(GLINK_LEX Identifier) `,` $(GSELF Identifiers)
+
 $(GNAME AliasAssignments):
     $(GLINK AliasAssignment)
     $(GSELF AliasAssignments) $(D ,) $(GLINK AliasAssignment)