157 lines
5.1 KiB
Rust
157 lines
5.1 KiB
Rust
// Shorthand template application desugaring for NIR
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//
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// Copyright (C) 2014-2023 Ryan Specialty, LLC.
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//
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// This file is part of TAME.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//! Shorthand template application desugaring for NIR.
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//!
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//! A shorthand template application looks something like this,
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//! in XML form:
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//!
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//! ```xml
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//! <t:foo bar="baz">
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//! <c:sum />
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//! </t:foo>
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//!
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//! <!-- desugars into -->
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//! <apply-template name="_foo_">
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//! <with-param name="@bar@" value="baz" />
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//! <with-param name="@values@">
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//! <c:sum />
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//! </with-param>
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//! </apply-template>
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//! ```
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//!
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//! The shorthand syntax makes templates look like another language
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//! primitive,
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//! with the exception of the namespace prefix.
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//!
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//! Note how desugaring also wraps template names in `'_'` and param names
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//! in `'@'`.
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//! These naming requirements were intended to eliminate conflicts with
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//! other types of identifiers and to make it obvious when templates and
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//! metavariables were being used,
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//! but it works against the goal of making template applications look
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//! like language primitives.
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//! Shorthand form was added well after the long `apply-template` form.
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//!
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//! This shorthand version does not permit metavariables for template or
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//! param names,
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//! so the long form is still a useful language feature for more
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//! sophisticated cases.
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//!
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//! This was originally handled in the XSLT compiler in
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//! `:src/current/include/preproc/template.xsl`.
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//! You may need to consult the Git history if this file is no longer
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//! available or if the XSLT template was since removed.
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use arrayvec::ArrayVec;
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use super::{Nir, NirEntity};
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use crate::{
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parse::prelude::*,
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sym::{GlobalSymbolIntern, GlobalSymbolResolve},
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};
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use std::convert::Infallible;
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#[derive(Debug, PartialEq, Eq, Default)]
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pub enum TplShortDesugar {
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/// Waiting for shorthand template application,
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/// passing tokens along in the meantime.
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#[default]
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Scanning,
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}
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impl Display for TplShortDesugar {
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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match self {
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Self::Scanning => {
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write!(f, "awaiting shorthand template application")
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}
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}
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}
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}
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impl ParseState for TplShortDesugar {
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type Token = Nir;
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type Object = Nir;
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type Error = Infallible;
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type Context = Stack;
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fn parse_token(
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self,
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tok: Self::Token,
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stack: &mut Self::Context,
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) -> TransitionResult<Self::Super> {
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use TplShortDesugar::*;
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if let Some(obj) = stack.pop() {
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return Transition(self).ok(obj).with_lookahead(tok);
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}
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match (self, tok) {
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// Shorthand template applications are identified by a `Some`
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// QName in the `TplApply` entity.
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//
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// The name of the template _without_ the underscore padding is
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// the local part of the QName.
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(Scanning, Nir::Open(NirEntity::TplApply(Some(qname)), span)) => {
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// TODO: Determine whether caching these has any notable
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// benefit over repeated heap allocations,
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// comparing packages with very few applications and
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// packages with thousands
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// (we'd still have to hit the heap for the cache).
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let tpl_name =
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format!("_{}_", qname.local_name().lookup_str()).intern();
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stack.push(Nir::Ref(SPair(tpl_name, span)));
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Transition(Scanning)
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.ok(Nir::Open(NirEntity::TplApply(None), span))
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}
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// Shorthand template params' names do not contain the
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// surrounding `@`s.
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(
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Scanning,
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Nir::Open(NirEntity::TplParam(Some((name, val))), span),
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) => {
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let pname = format!("@{name}@").intern();
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stack.push(Nir::Close(NirEntity::TplParam(None), span));
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stack.push(Nir::Text(val));
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stack.push(Nir::BindIdent(SPair(pname, name.span())));
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Transition(Scanning)
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.ok(Nir::Open(NirEntity::TplParam(None), span))
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}
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// Any tokens that we don't recognize will be passed on unchanged.
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(st, tok) => Transition(st).ok(tok),
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}
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}
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fn is_accepting(&self, stack: &Self::Context) -> bool {
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matches!(self, Self::Scanning) && stack.is_empty()
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}
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}
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type Stack = ArrayVec<Nir, 3>;
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#[cfg(test)]
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mod test;
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