diff --git a/sv-parser-macros/src/lib.rs b/sv-parser-macros/src/lib.rs
index 718781a..d73dafe 100644
--- a/sv-parser-macros/src/lib.rs
+++ b/sv-parser-macros/src/lib.rs
@@ -4,9 +4,8 @@ extern crate proc_macro;
 
 use crate::proc_macro::TokenStream;
 use quote::quote;
-use std::str::FromStr;
 use syn::Data::{Enum, Struct};
-use syn::{self, parse_macro_input, AttributeArgs, DeriveInput, ItemFn, Meta, NestedMeta, Stmt};
+use syn::{self, DeriveInput};
 
 #[proc_macro_derive(Node)]
 pub fn node_derive(input: TokenStream) -> TokenStream {
@@ -155,120 +154,3 @@ fn impl_ref_node(ast: &DeriveInput) -> TokenStream {
     };
     gen.into()
 }
-
-#[proc_macro_attribute]
-pub fn parser(attr: TokenStream, item: TokenStream) -> TokenStream {
-    let attr = parse_macro_input!(attr as AttributeArgs);
-    let item = parse_macro_input!(item as ItemFn);
-    impl_parser(&attr, &item)
-}
-
-fn impl_parser(attr: &AttributeArgs, item: &ItemFn) -> TokenStream {
-    let ambiguous = impl_parser_attribute(attr);
-
-    let body = if ambiguous {
-        impl_parser_body_ambiguous(&item)
-    } else {
-        impl_parser_body(&item)
-    };
-    let body = parse_macro_input!(body as Stmt);
-
-    let mut item = item.clone();
-
-    item.block.stmts.clear();
-    item.block.stmts.push(body);
-
-    let gen = quote! {
-        #item
-    };
-    gen.into()
-}
-
-fn impl_parser_attribute(attr: &AttributeArgs) -> bool {
-    let mut ambiguous = false;
-
-    for a in attr {
-        match a {
-            NestedMeta::Meta(Meta::Word(x)) if x == "Ambiguous" => ambiguous = true,
-            _ => panic!(),
-        }
-    }
-
-    ambiguous
-}
-
-fn impl_parser_body(item: &ItemFn) -> TokenStream {
-    let mut gen = quote! {};
-    for s in &item.block.stmts {
-        gen = quote! {
-            #gen
-            #s
-        };
-    }
-    let gen = quote! {
-        {
-            #gen
-        }
-    };
-    gen.into()
-}
-
-fn impl_parser_body_ambiguous(item: &ItemFn) -> TokenStream {
-    let mut token = quote! {};
-    for s in &item.block.stmts {
-        token = quote! {
-            #token
-            #s
-        };
-    }
-    let mut token = token.to_string();
-
-    let ambiguous_cnt: Vec<&str> = token.matches("ambiguous").collect();
-    let ambiguous_cnt = ambiguous_cnt.len();
-
-    let mut replace_parsers = Vec::new();
-    for i in 0..ambiguous_cnt {
-        let pos = token.find("ambiguous").unwrap();
-        let (head, rest) = token.split_at(pos);
-        if rest.starts_with("ambiguous_opt") {
-            let rest = rest.replacen("ambiguous_opt", &format!("amb_temporary{}", i), 1);
-            token = format!("{}{}", head, rest);
-            replace_parsers.push(("opt", "none"));
-        } else if rest.starts_with("ambiguous_alt") {
-            let rest = rest.replacen("ambiguous_alt", &format!("amb_temporary{}", i), 1);
-            token = format!("{}{}", head, rest);
-            replace_parsers.push(("alt_left", "alt_right"));
-        }
-    }
-
-    let mut gen = quote! {};
-    for i in 0..2_u32.pow(ambiguous_cnt as u32) {
-        let mut token = token.clone();
-        for j in 0..ambiguous_cnt {
-            let (p0, p1) = replace_parsers[j];
-            let repl = if ((i >> j) & 1) == 0 { p0 } else { p1 };
-            token = token.replace(&format!("amb_temporary{}", j), repl);
-        }
-        let token = format!("{{ {} }}", token);
-        let token = TokenStream::from_str(&token).unwrap();
-        let token = parse_macro_input!(token as Stmt);
-        gen = quote! {
-            #gen
-            |s| #token,
-        };
-    }
-
-    let gen = quote! {
-        alt((
-            #gen
-        ))(s)
-    };
-
-    let gen = quote! {
-        {
-            #gen
-        }
-    };
-
-    gen.into()
-}
diff --git a/sv-parser-parser/Cargo.toml b/sv-parser-parser/Cargo.toml
index 2464b2d..00a0d49 100644
--- a/sv-parser-parser/Cargo.toml
+++ b/sv-parser-parser/Cargo.toml
@@ -11,6 +11,7 @@ trace   = ["nom-tracable/trace"]
 [dependencies]
 nom                  = "5.0.0"
 nom_locate           = "0.4.0"
+nom-both             = {path = "../../nom-both/nom-both"}
 nom-packrat          = {path = "../../nom-packrat/nom-packrat"}
 nom-recursive        = {path = "../../nom-recursive/nom-recursive"}
 nom-tracable         = {path = "../../nom-tracable/nom-tracable"}
diff --git a/sv-parser-parser/src/declarations/assertion_declarations.rs b/sv-parser-parser/src/declarations/assertion_declarations.rs
index 6b3672a..e91968b 100644
--- a/sv-parser-parser/src/declarations/assertion_declarations.rs
+++ b/sv-parser-parser/src/declarations/assertion_declarations.rs
@@ -234,12 +234,12 @@ pub(crate) fn property_port_list(s: Span) -> IResult<Span, PropertyPortList> {
     Ok((s, PropertyPortList { nodes: (a,) }))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn property_port_item(s: Span) -> IResult<Span, PropertyPortItem> {
     let (s, a) = many0(attribute_instance)(s)?;
     let (s, b) = opt(pair(local, opt(property_lvar_port_direction)))(s)?;
-    let (s, c) = ambiguous_opt(property_formal_type)(s)?;
+    let (s, c) = both_opt(property_formal_type)(s)?;
     let (s, d) = formal_port_identifier(s)?;
     let (s, e) = many0(variable_dimension)(s)?;
     let (s, f) = opt(pair(symbol("="), property_actual_arg))(s)?;
@@ -724,12 +724,12 @@ pub(crate) fn sequence_port_list(s: Span) -> IResult<Span, SequencePortList> {
     Ok((s, SequencePortList { nodes: (a,) }))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn sequence_port_item(s: Span) -> IResult<Span, SequencePortItem> {
     let (s, a) = many0(attribute_instance)(s)?;
     let (s, b) = opt(pair(local, opt(sequence_lvar_port_direction)))(s)?;
-    let (s, c) = ambiguous_opt(sequence_formal_type)(s)?;
+    let (s, c) = both_opt(sequence_formal_type)(s)?;
     let (s, d) = formal_port_identifier(s)?;
     let (s, e) = many0(variable_dimension)(s)?;
     let (s, f) = opt(pair(symbol("="), sequence_actual_arg))(s)?;
diff --git a/sv-parser-parser/src/declarations/covergroup_declarations.rs b/sv-parser-parser/src/declarations/covergroup_declarations.rs
index 438d5df..5437f2e 100644
--- a/sv-parser-parser/src/declarations/covergroup_declarations.rs
+++ b/sv-parser-parser/src/declarations/covergroup_declarations.rs
@@ -206,11 +206,11 @@ pub(crate) fn hierarchical_identifier_or_class_scope(
     ))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn cover_point(s: Span) -> IResult<Span, CoverPoint> {
     let (s, a) = opt(triple(
-        ambiguous_opt(data_type_or_implicit),
+        both_opt(data_type_or_implicit),
         cover_point_identifier,
         symbol(":"),
     ))(s)?;
diff --git a/sv-parser-parser/src/declarations/function_declarations.rs b/sv-parser-parser/src/declarations/function_declarations.rs
index 19e9cd7..559b6ac 100644
--- a/sv-parser-parser/src/declarations/function_declarations.rs
+++ b/sv-parser-parser/src/declarations/function_declarations.rs
@@ -30,12 +30,12 @@ pub(crate) fn function_body_declaration(s: Span) -> IResult<Span, FunctionBodyDe
     ))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn function_body_declaration_without_port(
     s: Span,
 ) -> IResult<Span, FunctionBodyDeclaration> {
-    let (s, a) = ambiguous_opt(function_data_type_or_implicit)(s)?;
+    let (s, a) = both_opt(function_data_type_or_implicit)(s)?;
     let (s, b) = opt(interface_identifier_or_class_scope)(s)?;
     let (s, c) = function_identifier(s)?;
     let (s, d) = symbol(";")(s)?;
@@ -51,12 +51,12 @@ pub(crate) fn function_body_declaration_without_port(
     ))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn function_body_declaration_with_port(
     s: Span,
 ) -> IResult<Span, FunctionBodyDeclaration> {
-    let (s, a) = ambiguous_opt(function_data_type_or_implicit)(s)?;
+    let (s, a) = both_opt(function_data_type_or_implicit)(s)?;
     let (s, b) = opt(interface_identifier_or_class_scope)(s)?;
     let (s, c) = function_identifier(s)?;
     let (s, d) = paren(opt(tf_port_list))(s)?;
diff --git a/sv-parser-parser/src/declarations/let_declarations.rs b/sv-parser-parser/src/declarations/let_declarations.rs
index 5313623..13c854e 100644
--- a/sv-parser-parser/src/declarations/let_declarations.rs
+++ b/sv-parser-parser/src/declarations/let_declarations.rs
@@ -30,11 +30,11 @@ pub(crate) fn let_port_list(s: Span) -> IResult<Span, LetPortList> {
     Ok((s, LetPortList { nodes: (a,) }))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn let_port_item(s: Span) -> IResult<Span, LetPortItem> {
     let (s, a) = many0(attribute_instance)(s)?;
-    let (s, b) = ambiguous_opt(let_formal_type)(s)?;
+    let (s, b) = both_opt(let_formal_type)(s)?;
     let (s, c) = formal_port_identifier(s)?;
     let (s, d) = many0(variable_dimension)(s)?;
     let (s, e) = opt(pair(symbol("="), expression))(s)?;
diff --git a/sv-parser-parser/src/declarations/module_parameter_declarations.rs b/sv-parser-parser/src/declarations/module_parameter_declarations.rs
index d4fbbf7..38a699d 100644
--- a/sv-parser-parser/src/declarations/module_parameter_declarations.rs
+++ b/sv-parser-parser/src/declarations/module_parameter_declarations.rs
@@ -10,13 +10,13 @@ pub(crate) fn local_parameter_declaration(s: Span) -> IResult<Span, LocalParamet
     ))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn local_parameter_declaration_param(
     s: Span,
 ) -> IResult<Span, LocalParameterDeclaration> {
     let (s, a) = keyword("localparam")(s)?;
-    let (s, b) = ambiguous_opt(data_type_or_implicit)(s)?;
+    let (s, b) = both_opt(data_type_or_implicit)(s)?;
     let (s, c) = list_of_param_assignments(s)?;
     Ok((
         s,
@@ -46,11 +46,11 @@ pub(crate) fn parameter_declaration(s: Span) -> IResult<Span, ParameterDeclarati
     alt((parameter_declaration_param, parameter_declaration_type))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn parameter_declaration_param(s: Span) -> IResult<Span, ParameterDeclaration> {
     let (s, a) = keyword("parameter")(s)?;
-    let (s, b) = ambiguous_opt(data_type_or_implicit)(s)?;
+    let (s, b) = both_opt(data_type_or_implicit)(s)?;
     let (s, c) = list_of_param_assignments(s)?;
     Ok((
         s,
diff --git a/sv-parser-parser/src/declarations/port_declarations.rs b/sv-parser-parser/src/declarations/port_declarations.rs
index 956b4ed..d2baa6f 100644
--- a/sv-parser-parser/src/declarations/port_declarations.rs
+++ b/sv-parser-parser/src/declarations/port_declarations.rs
@@ -2,11 +2,11 @@ use crate::*;
 
 // -----------------------------------------------------------------------------
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn inout_declaration(s: Span) -> IResult<Span, InoutDeclaration> {
     let (s, a) = keyword("inout")(s)?;
-    let (s, b) = ambiguous_opt(net_port_type)(s)?;
+    let (s, b) = both_opt(net_port_type)(s)?;
     let (s, c) = list_of_port_identifiers(s)?;
     Ok((s, InoutDeclaration { nodes: (a, b, c) }))
 }
@@ -16,11 +16,11 @@ pub(crate) fn input_declaration(s: Span) -> IResult<Span, InputDeclaration> {
     alt((input_declaration_net, input_declaration_variable))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn input_declaration_net(s: Span) -> IResult<Span, InputDeclaration> {
     let (s, a) = keyword("input")(s)?;
-    let (s, b) = ambiguous_opt(net_port_type)(s)?;
+    let (s, b) = both_opt(net_port_type)(s)?;
     let (s, c) = list_of_port_identifiers(s)?;
     Ok((
         s,
@@ -28,11 +28,11 @@ pub(crate) fn input_declaration_net(s: Span) -> IResult<Span, InputDeclaration>
     ))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn input_declaration_variable(s: Span) -> IResult<Span, InputDeclaration> {
     let (s, a) = keyword("input")(s)?;
-    let (s, b) = ambiguous_alt(variable_port_type, implicit_var)(s)?;
+    let (s, b) = both_alt(variable_port_type, implicit_var)(s)?;
     let (s, c) = list_of_variable_identifiers(s)?;
     Ok((
         s,
@@ -45,11 +45,11 @@ pub(crate) fn output_declaration(s: Span) -> IResult<Span, OutputDeclaration> {
     alt((output_declaration_net, output_declaration_variable))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn output_declaration_net(s: Span) -> IResult<Span, OutputDeclaration> {
     let (s, a) = keyword("output")(s)?;
-    let (s, b) = ambiguous_opt(net_port_type)(s)?;
+    let (s, b) = both_opt(net_port_type)(s)?;
     let (s, c) = list_of_port_identifiers(s)?;
     Ok((
         s,
@@ -57,11 +57,11 @@ pub(crate) fn output_declaration_net(s: Span) -> IResult<Span, OutputDeclaration
     ))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn output_declaration_variable(s: Span) -> IResult<Span, OutputDeclaration> {
     let (s, a) = keyword("output")(s)?;
-    let (s, b) = ambiguous_alt(variable_port_type, implicit_var)(s)?;
+    let (s, b) = both_alt(variable_port_type, implicit_var)(s)?;
     let (s, c) = list_of_variable_port_identifiers(s)?;
     Ok((
         s,
@@ -77,11 +77,11 @@ pub(crate) fn interface_port_declaration(s: Span) -> IResult<Span, InterfacePort
     Ok((s, InterfacePortDeclaration { nodes: (a, b, c) }))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn ref_declaration(s: Span) -> IResult<Span, RefDeclaration> {
     let (s, a) = keyword("ref")(s)?;
-    let (s, b) = ambiguous_alt(variable_port_type, implicit_var)(s)?;
+    let (s, b) = both_alt(variable_port_type, implicit_var)(s)?;
     let (s, c) = list_of_variable_identifiers(s)?;
     Ok((s, RefDeclaration { nodes: (a, b, c) }))
 }
diff --git a/sv-parser-parser/src/declarations/task_declarations.rs b/sv-parser-parser/src/declarations/task_declarations.rs
index dc6bd31..5c6798d 100644
--- a/sv-parser-parser/src/declarations/task_declarations.rs
+++ b/sv-parser-parser/src/declarations/task_declarations.rs
@@ -71,13 +71,13 @@ pub(crate) fn tf_port_list(s: Span) -> IResult<Span, TfPortList> {
     Ok((s, TfPortList { nodes: (a,) }))
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn tf_port_item(s: Span) -> IResult<Span, TfPortItem> {
     let (s, a) = many0(attribute_instance)(s)?;
     let (s, b) = opt(tf_port_direction)(s)?;
     let (s, c) = opt(var)(s)?;
-    let (s, d) = ambiguous_opt(data_type_or_implicit)(s)?;
+    let (s, d) = both_opt(data_type_or_implicit)(s)?;
     let (s, e) = opt(triple(
         port_identifier,
         many0(variable_dimension),
@@ -103,13 +103,13 @@ pub(crate) fn tf_port_direction(s: Span) -> IResult<Span, TfPortDirection> {
     ))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn tf_port_declaration(s: Span) -> IResult<Span, TfPortDeclaration> {
     let (s, a) = many0(attribute_instance)(s)?;
     let (s, b) = tf_port_direction(s)?;
     let (s, c) = opt(var)(s)?;
-    let (s, d) = ambiguous_opt(data_type_or_implicit)(s)?;
+    let (s, d) = both_opt(data_type_or_implicit)(s)?;
     let (s, e) = list_of_tf_variable_identifiers(s)?;
     let (s, f) = symbol(";")(s)?;
     Ok((
diff --git a/sv-parser-parser/src/declarations/type_declarations.rs b/sv-parser-parser/src/declarations/type_declarations.rs
index f012563..c188806 100644
--- a/sv-parser-parser/src/declarations/type_declarations.rs
+++ b/sv-parser-parser/src/declarations/type_declarations.rs
@@ -18,13 +18,13 @@ pub(crate) fn data_declaration(s: Span) -> IResult<Span, DataDeclaration> {
     ))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn data_declaration_variable(s: Span) -> IResult<Span, DataDeclaration> {
     let (s, a) = opt(r#const)(s)?;
     let (s, b) = opt(var)(s)?;
     let (s, c) = opt(lifetime)(s)?;
-    let (s, d) = ambiguous_opt(data_type_or_implicit)(s)?;
+    let (s, d) = both_opt(data_type_or_implicit)(s)?;
     let (s, e) = list_of_variable_decl_assignments(s)?;
     let (s, f) = symbol(";")(s)?;
     Ok((
@@ -127,13 +127,13 @@ pub(crate) fn net_declaration(s: Span) -> IResult<Span, NetDeclaration> {
     ))(s)
 }
 
-#[parser(Ambiguous)]
+#[both_parser]
 #[tracable_parser]
 pub(crate) fn net_declaration_net_type(s: Span) -> IResult<Span, NetDeclaration> {
     let (s, a) = net_type(s)?;
     let (s, b) = opt(strength)(s)?;
     let (s, c) = opt(vector_scalar)(s)?;
-    let (s, d) = ambiguous_opt(data_type_or_implicit)(s)?;
+    let (s, d) = both_opt(data_type_or_implicit)(s)?;
     let (s, e) = opt(delay3)(s)?;
     let (s, f) = list_of_net_decl_assignments(s)?;
     let (s, g) = symbol(";")(s)?;
diff --git a/sv-parser-parser/src/lib.rs b/sv-parser-parser/src/lib.rs
index 34b2247..5e4bbcf 100644
--- a/sv-parser-parser/src/lib.rs
+++ b/sv-parser-parser/src/lib.rs
@@ -31,12 +31,12 @@ pub(crate) use nom::error::{make_error, ErrorKind};
 pub(crate) use nom::multi::*;
 pub(crate) use nom::sequence::*;
 pub(crate) use nom::{Err, IResult};
+pub(crate) use nom_both::both_parser;
 pub(crate) use nom_packrat::{self, packrat_parser, HasExtraState};
 pub(crate) use nom_recursive::{recursive_parser, HasRecursiveInfo, RecursiveInfo};
 pub(crate) use nom_tracable::tracable_parser;
 #[cfg(feature = "trace")]
 pub(crate) use nom_tracable::{HasTracableInfo, TracableInfo};
-pub(crate) use sv_parser_macros::*;
 pub(crate) use sv_parser_syntaxtree::*;
 
 // -----------------------------------------------------------------------------
diff --git a/sv-parser-parser/src/utils.rs b/sv-parser-parser/src/utils.rs
index 4d9ef65..3f38437 100644
--- a/sv-parser-parser/src/utils.rs
+++ b/sv-parser-parser/src/utils.rs
@@ -495,35 +495,6 @@ where
     }
 }
 
-pub(crate) fn none<'a, O, F>(_f: F) -> impl Fn(Span<'a>) -> IResult<Span<'a>, Option<O>>
-where
-    F: Fn(Span<'a>) -> IResult<Span<'a>, O>,
-{
-    move |s: Span<'a>| Ok((s, None))
-}
-
-pub(crate) fn alt_left<'a, O, F, G>(f: F, _g: G) -> impl Fn(Span<'a>) -> IResult<Span<'a>, O>
-where
-    F: Fn(Span<'a>) -> IResult<Span<'a>, O>,
-    G: Fn(Span<'a>) -> IResult<Span<'a>, O>,
-{
-    move |s: Span<'a>| {
-        let (s, x) = f(s)?;
-        Ok((s, x))
-    }
-}
-
-pub(crate) fn alt_right<'a, O, F, G>(_f: F, g: G) -> impl Fn(Span<'a>) -> IResult<Span<'a>, O>
-where
-    F: Fn(Span<'a>) -> IResult<Span<'a>, O>,
-    G: Fn(Span<'a>) -> IResult<Span<'a>, O>,
-{
-    move |s: Span<'a>| {
-        let (s, x) = g(s)?;
-        Ok((s, x))
-    }
-}
-
 // -----------------------------------------------------------------------------
 
 #[tracable_parser]