Add explicit "pure" to the syntax parser

The "pure" keyword was previously added to the tokenizer only.
Extending the syntax parser with "Pure" where "Impure" was used allows
for parsing explicit pure functions correctly.

Author: HenningHolmDE

vhdl_lang/src/syntax/declarative_part.rs

@@ -50,13 +50,13 @@ pub fn is_declarative_part(stream: &mut TokenStream, begin_is_end: bool) -> Pars
 fn check_declarative_part(token: &Token, may_end: bool, may_begin: bool) -> ParseResult<()> {
     match token.kind {
         Use | Type | Subtype | Shared | Constant | Signal | Variable | File | Component
-        | Attribute | Alias | Impure | Function | Procedure | Package | For => Ok(()),
+        | Attribute | Alias | Impure | Pure | Function | Procedure | Package | For => Ok(()),
         Begin if may_begin => Ok(()),
         End if may_end => Ok(()),
         _ => {
             let decl_kinds = [
                 Use, Type, Subtype, Shared, Constant, Signal, Variable, File, Component, Attribute,
-                Alias, Impure, Function, Procedure, Package, For,
+                Alias, Impure, Pure, Function, Procedure, Package, For,
             ];
 
             Err(token.kinds_error(&decl_kinds))
@@ -83,23 +83,23 @@ pub fn parse_declarative_part_leave_end_token(
 
     fn is_recover_token(kind: Kind) -> bool {
         match kind {
-            Type | Subtype | Component | Impure | Function | Procedure | Package | For | File
-            | Shared | Constant | Signal | Variable | Attribute | Use | Alias => true,
+            Type | Subtype | Component | Impure | Pure | Function | Procedure | Package | For
+            | File | Shared | Constant | Signal | Variable | Attribute | Use | Alias => true,
             _ => false,
         }
     };
 
     while let Some(token) = stream.peek()? {
         match token.kind {
             Begin | End => break,
-            Type | Subtype | Component | Impure | Function | Procedure | Package | For => {
+            Type | Subtype | Component | Impure | Pure | Function | Procedure | Package | For => {
                 let decl = match token.kind {
                     Type | Subtype => {
                         parse_type_declaration(stream, diagnostics).map(Declaration::Type)?
                     }
                     Component => parse_component_declaration(stream, diagnostics)
                         .map(Declaration::Component)?,
-                    Impure | Function | Procedure => parse_subprogram(stream, diagnostics)?,
+                    Impure | Pure | Function | Procedure => parse_subprogram(stream, diagnostics)?,
                     Package => parse_package_instantiation(stream).map(Declaration::Package)?,
                     For => {
                         parse_configuration_specification(stream).map(Declaration::Configuration)?
@@ -145,8 +145,8 @@ pub fn parse_declarative_part_leave_end_token(
 
             _ => {
                 diagnostics.push(token.kinds_error(&[
-                    Type, Subtype, Component, Impure, Function, Procedure, Package, For, File,
-                    Shared, Constant, Signal, Variable, Attribute, Use, Alias,
+                    Type, Subtype, Component, Impure, Pure, Function, Procedure, Package, For,
+                    File, Shared, Constant, Signal, Variable, Attribute, Use, Alias,
                 ]));
                 stream.skip_until(is_recover_token)?;
                 continue;
@@ -232,7 +232,7 @@ constant x: natural := 5;
             msgs,
             vec![Diagnostic::error(
                 code.s1("var").pos(),
-                "Expected 'type', 'subtype', 'component', 'impure', \
+                "Expected 'type', 'subtype', 'component', 'impure', 'pure', \
                  'function', 'procedure', 'package', 'for', 'file', \
                  'shared', 'constant', 'signal', 'variable', 'attribute', \
                  'use' or 'alias'"

vhdl_lang/src/syntax/interface_declaration.rs

@@ -227,7 +227,7 @@ fn parse_interface_declaration(
             let ident = stream.expect_ident()?;
             Ok(vec![InterfaceDeclaration::Type(ident)])
         },
-        Function | Procedure | Impure => {
+        Function | Procedure | Impure | Pure => {
             let decl = parse_subprogram_declaration_no_semi(stream, diagnostics)?;
             let default = parse_subprogram_default(stream)?;