735 lines
24 KiB
Rust
735 lines
24 KiB
Rust
// ASG IR
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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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//! Intermediate representation for construction of the
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//! [abstract semantic graph (ASG)](super) (AIR).
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//!
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//! AIR serves as an abstraction layer between higher-level parsers and the
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//! aggregate ASG.
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//! It allows parsers to operate as a raw stream of data without having to
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//! worry about ownership of or references to the ASG,
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//! and allows for multiple such parsers to be joined.
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//!
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//! AIR is _not_ intended to replace the API of the ASG---it
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//! is intended as a termination point for the parsing pipeline,
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//! and as such implements a subset of the ASG's API that is suitable
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//! for aggregating raw data from source and object files.
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//! Given that it does so little and is so close to the [`Asg`] API,
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//! one might say that the abstraction is as light as air,
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//! but that would surely result in face-palming and so we're not going
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//! air such cringeworthy dad jokes here.
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use super::{
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graph::object::{Object, ObjectIndexTo, ObjectIndexToTree, Pkg, Tpl},
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Asg, AsgError, Expr, Ident, ObjectIndex,
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};
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use crate::{
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f::Functor,
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parse::{prelude::*, StateStack},
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span::Span,
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sym::SymbolId,
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};
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use std::fmt::{Debug, Display};
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#[macro_use]
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mod ir;
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pub use ir::Air;
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mod expr;
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mod pkg;
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mod tpl;
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use expr::AirExprAggregate;
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use pkg::AirPkgAggregate;
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use tpl::AirTplAggregate;
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pub type IdentSym = SymbolId;
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pub type DepSym = SymbolId;
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/// AIR parser state.
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#[derive(Debug, PartialEq, Default)]
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pub enum AirAggregate {
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/// Parser is in the root context.
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///
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/// As a parser,
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/// this does nothing but await work.
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/// Its presence in the [`AirStack`] is used for the global environment.
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#[default]
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Root,
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/// Parsing a package.
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Pkg(AirPkgAggregate),
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/// Parsing an expression.
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///
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/// This expects to inherit an [`AirExprAggregate`] from the prior state
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/// so that we are not continuously re-allocating its stack for each
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/// new expression root.
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PkgExpr(AirExprAggregate),
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/// Parser is in template parsing mode.
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///
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/// All objects encountered until the closing [`Air::TplEnd`] will be
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/// parented to this template rather than the parent [`Pkg`].
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/// See [`Air::TplStart`] for more information.
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PkgTpl(AirTplAggregate),
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}
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impl Display for AirAggregate {
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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use AirAggregate::*;
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match self {
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Root => write!(f, "awaiting AIR input for ASG"),
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Pkg(pkg) => {
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write!(f, "defining a package: {pkg}")
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}
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PkgExpr(expr) => {
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write!(f, "defining a package expression: {expr}")
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}
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PkgTpl(tpl) => {
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write!(f, "building a template: {tpl}",)
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}
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}
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}
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}
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impl From<AirPkgAggregate> for AirAggregate {
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fn from(st: AirPkgAggregate) -> Self {
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Self::Pkg(st)
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}
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}
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impl From<AirExprAggregate> for AirAggregate {
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fn from(st: AirExprAggregate) -> Self {
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Self::PkgExpr(st)
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}
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}
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impl From<AirTplAggregate> for AirAggregate {
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fn from(st: AirTplAggregate) -> Self {
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Self::PkgTpl(st)
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}
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}
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impl ParseState for AirAggregate {
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type Token = Air;
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type Object = ();
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type Error = AsgError;
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type Context = AirAggregateCtx;
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/// Destination [`Asg`] that this parser lowers into.
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///
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/// This ASG will be yielded by [`crate::parse::Parser::finalize`].
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type PubContext = Asg;
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fn parse_token(
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self,
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tok: Self::Token,
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ctx: &mut Self::Context,
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) -> crate::parse::TransitionResult<Self> {
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use ir::{AirSubsets::*, AirTodo::*};
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use AirAggregate::*;
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match (self, tok.into()) {
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(st, AirTodo(Todo(_))) => Transition(st).incomplete(),
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// Package
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(st @ (Root | PkgExpr(..) | PkgTpl(..)), tok @ AirPkg(..)) => {
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ctx.ret_or_transfer(st, tok, AirPkgAggregate::new())
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}
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(Pkg(pkg), AirPkg(etok)) => ctx.proxy(pkg, etok),
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(Pkg(pkg), AirBind(etok)) => ctx.proxy(pkg, etok),
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(Pkg(pkg), AirIdent(etok)) => ctx.proxy(pkg, etok),
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(Pkg(pkg), AirDoc(etok)) => ctx.proxy(pkg, etok),
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// Expression
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(st @ (Pkg(_) | PkgTpl(_)), tok @ AirExpr(..)) => {
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ctx.ret_or_transfer(st, tok, AirExprAggregate::new())
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}
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(PkgExpr(expr), AirExpr(etok)) => ctx.proxy(expr, etok),
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(PkgExpr(expr), AirBind(etok)) => ctx.proxy(expr, etok),
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(PkgExpr(expr), AirDoc(etok)) => ctx.proxy(expr, etok),
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// Template
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(st @ (Pkg(_) | PkgExpr(_)), tok @ AirTpl(..)) => {
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ctx.ret_or_transfer(st, tok, AirTplAggregate::new())
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}
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(PkgTpl(tplst), AirTpl(ttok)) => ctx.proxy(tplst, ttok),
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(PkgTpl(tplst), AirBind(ttok)) => ctx.proxy(tplst, ttok),
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(PkgTpl(tplst), AirDoc(ttok)) => ctx.proxy(tplst, ttok),
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(
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Root,
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tok @ (AirExpr(..) | AirBind(..) | AirTpl(..) | AirDoc(..)),
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) => Transition(Root).err(AsgError::PkgExpected(tok.span())),
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(st @ (Root | PkgExpr(..) | PkgTpl(..)), AirIdent(tok)) => {
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Transition(st).err(AsgError::UnexpectedOpaqueIdent(tok.name()))
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}
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}
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}
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fn is_accepting(&self, ctx: &Self::Context) -> bool {
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ctx.stack_ref().iter().all(|st| st.active_is_accepting(ctx))
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&& self.active_is_accepting(ctx)
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}
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}
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impl AirAggregate {
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/// Whether the active parser is completed with active parsing.
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///
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/// This method is used to determine whether control ought to be
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/// transferred to a new child parser.
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///
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/// If a child parser is active,
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/// then its [`ParseState::is_accepting`] will be consulted.
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fn active_is_complete(&self, ctx: &<Self as ParseState>::Context) -> bool {
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use AirAggregate::*;
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match self {
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// We can't be done with something we're not doing.
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// This is necessary to start the first child parser.
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Root => false,
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Pkg(st) => st.is_accepting(ctx),
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PkgExpr(st) => st.is_accepting(ctx),
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PkgTpl(st) => st.is_accepting(ctx),
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}
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}
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// Whether the parser is in an accepting state.
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fn active_is_accepting(&self, ctx: &<Self as ParseState>::Context) -> bool {
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use AirAggregate::*;
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match self {
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// This must not recurse on `AirAggregate::is_accepting`,
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// otherwise it'll be mutually recursive.
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Root => true,
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Pkg(st) => st.is_accepting(ctx),
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PkgExpr(st) => st.is_accepting(ctx),
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PkgTpl(st) => st.is_accepting(ctx),
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}
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}
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/// The rooting context for [`Ident`]s for the active parser.
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///
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/// A value of [`None`] indicates that the current parser does not
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/// support direct bindings,
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/// but a parent context may
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/// (see [`AirAggregateCtx::rooting_oi`]).
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fn active_rooting_oi(&self) -> Option<ObjectIndexToTree<Ident>> {
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match self {
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AirAggregate::Root => None,
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// Packages always serve as roots for identifiers
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// (that is their entire purpose).
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AirAggregate::Pkg(pkgst) => pkgst.active_pkg_oi().map(Into::into),
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// Expressions never serve as roots for identifiers;
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// this will always fall through to the parent context.
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// Since the parent context is a package or a template,
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// the next frame should succeed.
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AirAggregate::PkgExpr(_) => None,
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// Identifiers bound while within a template definition context
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// must bind to the eventual _expansion_ site,
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// as if the body were pasted there.
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// Templates must therefore serve as containers for identifiers
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// bound therein.
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AirAggregate::PkgTpl(tplst) => {
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tplst.active_tpl_oi().map(Into::into)
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}
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}
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}
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/// Adjust a [`EnvScopeKind`] while crossing an environment boundary
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/// into `self`.
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///
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/// An identifier is _visible_ at the environment in which it is defined.
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/// This identifier casts a _shadow_ to lower environments,
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/// with the exception of the root.
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/// The _root_ will absorb adjacent visible identifiers into a _pool_,
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/// which is distinct from the hierarchy that is otherwise created at
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/// the package level and lower.
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fn env_cross_boundary_into<T>(
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&self,
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kind: EnvScopeKind<T>,
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) -> EnvScopeKind<T> {
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use AirAggregate::*;
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use EnvScopeKind::*;
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match (self, kind) {
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// Hidden is a fixpoint.
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(_, kind @ Hidden(_)) => kind,
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// Expressions do not introduce their own environment
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// (they are not containers)
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// and so act as an identity function.
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(PkgExpr(_), kind) => kind,
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// A visible identifier will always cast a shadow in one step.
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// A shadow will always be cast (propagate) until the root.
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(Pkg(_) | PkgTpl(_), Visible(x) | Shadow(x)) => Shadow(x),
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// Above we see that Visual will always transition to Shadow in
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// one step.
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// Consequently,
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// Visible at Root means that we're a package-level Visible,
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// which must contribute to the pool.
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(Root, Visible(x)) => Visible(x),
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// If we're _not_ Visible at the root,
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// then we're _not_ a package-level definition,
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// and so we should _not_ contribute to the pool.
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(Root, Shadow(x)) => Hidden(x),
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}
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}
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}
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/// Additional parser context,
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/// including the ASG and parser stack frames.
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///
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/// [`ObjectIndex`] lookups perform reverse linear searches beginning from
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/// the last stack frame until a non-[`None`] value is found;
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/// this creates an environment whereby inner contexts shadow outer.
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/// Missing values create holes,
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/// much like a prototype chain.
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/// In practice,
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/// this should only have to search the last two frames.
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#[derive(Debug, Default)]
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pub struct AirAggregateCtx(Asg, AirStack, Option<ObjectIndex<Pkg>>);
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/// Limit of the maximum number of held parser frames.
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///
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/// Note that this is the number of [`ParseState`]s held,
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/// _not_ the depth of the graph at a given point.
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/// The intent of this is to limit runaway recursion in the event of some
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/// bug in the system;
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/// while the input stream is certainly finite,
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/// lookahead tokens cause recursion that does not provably
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/// terminate.
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///
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/// This limit is arbitrarily large,
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/// but hopefully such that no legitimate case will ever hit it.
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const MAX_AIR_STACK_DEPTH: usize = 1024;
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/// Held parser stack frames.
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///
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/// See [`AirAggregateCtx`] for more information.
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pub type AirStack = StateStack<AirAggregate, MAX_AIR_STACK_DEPTH>;
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impl AirAggregateCtx {
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fn asg_mut(&mut self) -> &mut Asg {
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self.as_mut()
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}
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fn asg_ref(&self) -> &Asg {
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self.as_ref()
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}
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fn stack(&mut self) -> &mut AirStack {
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let Self(_, stack, _) = self;
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stack
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}
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fn stack_ref(&self) -> &AirStack {
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let Self(_, stack, _) = self;
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stack
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}
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/// Return control to the parser atop of the stack if `st` is an
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/// accepting state,
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/// otherwise transfer control to a new parser `to`.
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///
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/// This serves as a balance with the behavior of [`Self::proxy`].
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/// Rather than checking for an accepting state after each proxy,
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/// or having the child parsers return to the top stack frame once
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/// they have completed,
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/// we leave the child parser in place to potentially handle more
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/// tokens of the same type.
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/// For example,
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/// adjacent expressions can re-use the same parser rather than having
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/// to pop and push for each sibling.
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///
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/// Consequently,
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/// this means that a parser may be complete when we need to push and
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/// transfer control to another parser.
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/// Before pushing,
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/// we first check to see if the parser atop of the stack is in an
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/// accepting state.
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/// If so,
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/// then we are a sibling,
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/// and so instead of proceeding with instantiating a new parser,
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/// we return to the one atop of the stack and delegate to it.
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///
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/// If `st` is _not_ in an accepting state,
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/// that means that we are a _child_;
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/// we then set aside the state `st` on the stack and transfer
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/// control to the child `to`.
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///
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/// See also [`Self::proxy`].
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fn ret_or_transfer<S: Into<AirAggregate>, SB: Into<AirAggregate>>(
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&mut self,
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st: S,
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tok: impl Token + Into<Air>,
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to: SB,
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) -> TransitionResult<AirAggregate> {
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let st_super = st.into();
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if st_super.active_is_complete(self) {
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// TODO: dead state or error
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self.stack().ret_or_dead(AirAggregate::Root, tok)
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} else {
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self.stack().transfer_with_ret(
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Transition(st_super),
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Transition(to.into()).incomplete().with_lookahead(tok),
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)
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}
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}
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/// Proxy `tok` to `st`,
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/// returning to the state atop of the stack if parsing reaches a dead
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/// state.
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///
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/// See also [`Self::ret_or_transfer`].
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fn proxy<S: ParseState<Super = AirAggregate, Context = Self>>(
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&mut self,
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st: S,
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tok: impl Token + Into<S::Token>,
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) -> TransitionResult<AirAggregate> {
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st.delegate_child(tok.into(), self, |_deadst, tok, ctx| {
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ctx.stack().ret_or_dead(AirAggregate::Root, tok)
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})
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}
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/// Create a new rooted package and record it as the active package.
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fn pkg_begin(
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&mut self,
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start: Span,
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name: SPair,
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) -> Result<ObjectIndex<Pkg>, AsgError> {
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let Self(asg, _, pkg) = self;
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let oi_root = asg.root(start);
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let oi_pkg = oi_root.create_pkg(asg, start, name)?;
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pkg.replace(oi_pkg);
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Ok(oi_pkg)
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}
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/// Indicate that there is no longer any active package.
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fn pkg_clear(&mut self) {
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let Self(_, _, pkg) = self;
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pkg.take();
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}
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/// The active package if any.
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fn pkg_oi(&self) -> Option<ObjectIndex<Pkg>> {
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match self {
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Self(_, _, oi) => *oi,
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}
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}
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/// The active container (rooting context) for [`Ident`]s.
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///
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/// The integer value returned represents the stack offset at which the
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/// rooting index was found,
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/// with `0` representing the package.
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///
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/// A value of [`None`] indicates that no bindings are permitted in the
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/// current context.
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fn rooting_oi(&self) -> Option<ObjectIndexToTree<Ident>> {
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let Self(_, stack, _) = self;
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stack.iter().rev().find_map(|st| st.active_rooting_oi())
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}
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/// The active dangling expression context for [`Expr`]s.
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///
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/// A value of [`None`] indicates that expressions are not permitted to
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/// dangle in the current context
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/// (and so must be identified).
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fn dangling_expr_oi(&self) -> Option<ObjectIndexTo<Expr>> {
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let Self(_, stack, _) = self;
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stack.iter().rev().find_map(|st| match st {
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AirAggregate::Root => None,
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// A dangling expression in a package context would be
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// unreachable.
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// There should be no parent frame and so this will fail to find
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// a value.
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AirAggregate::Pkg(_) => None,
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// Expressions may always contain other expressions,
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// and so this method should not be consulted in such a
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// context.
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// Nonetheless,
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// fall through to the parent frame and give a correct answer.
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AirAggregate::PkgExpr(_) => None,
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// Templates serve as containers for dangling expressions,
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// since they may expand into an context where they are not
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// considered to be dangling.
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AirAggregate::PkgTpl(tplst) => {
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tplst.active_tpl_oi().map(Into::into)
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}
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})
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}
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/// The active expansion target (splicing context) for [`Tpl`]s.
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///
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/// A value of [`None`] indicates that template expansion is not
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/// permitted in this current context.
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fn expansion_oi(&self) -> Option<ObjectIndexTo<Tpl>> {
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let Self(_, stack, _) = self;
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stack.iter().rev().find_map(|st| match st {
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AirAggregate::Root => None,
|
||
AirAggregate::Pkg(pkg_st) => pkg_st.active_pkg_oi().map(Into::into),
|
||
AirAggregate::PkgExpr(exprst) => {
|
||
exprst.active_expr_oi().map(Into::into)
|
||
}
|
||
AirAggregate::PkgTpl(tplst) => {
|
||
tplst.active_tpl_oi().map(Into::into)
|
||
}
|
||
})
|
||
}
|
||
|
||
/// Root an identifier using the [`Self::rooting_oi`] atop of the stack.
|
||
fn defines(&mut self, name: SPair) -> Result<ObjectIndex<Ident>, AsgError> {
|
||
let oi_root = self
|
||
.rooting_oi()
|
||
.ok_or(AsgError::InvalidBindContext(name))?;
|
||
|
||
Ok(self.lookup_lexical_or_missing(name).add_edge_from(
|
||
self.asg_mut(),
|
||
oi_root,
|
||
None,
|
||
))
|
||
}
|
||
|
||
/// Attempt to locate a lexically scoped identifier,
|
||
/// or create a new one if missing.
|
||
///
|
||
/// Since shadowing is not permitted
|
||
/// (but local identifiers are),
|
||
/// we can reduce the cost of lookups for the majority of identifiers
|
||
/// by beginning at the root and continuing down into the narrowest
|
||
/// lexical scope until we find what we're looking for.
|
||
///
|
||
/// Note that the global environment,
|
||
/// represented by the root,
|
||
/// is a pool of identifiers from all packages;
|
||
/// it does not form a hierarchy and local identifiers will not be
|
||
/// indexed outside of their package hierarchy,
|
||
/// so we'll have to continue searching for those.
|
||
fn lookup_lexical_or_missing(&mut self, name: SPair) -> ObjectIndex<Ident> {
|
||
let Self(asg, stack, _) = self;
|
||
|
||
stack
|
||
.iter()
|
||
.filter_map(|st| st.active_rooting_oi())
|
||
.find_map(|oi| asg.lookup(oi, name))
|
||
.unwrap_or_else(|| self.create_env_indexed_ident(name))
|
||
}
|
||
|
||
/// Index an identifier within its environment.
|
||
///
|
||
/// TODO: More information as this is formalized.
|
||
fn create_env_indexed_ident(&mut self, name: SPair) -> ObjectIndex<Ident> {
|
||
let Self(asg, stack, _) = self;
|
||
let oi_ident = asg.create(Ident::declare(name));
|
||
|
||
// TODO: This will need the active OI to support `AirIdent`s
|
||
stack
|
||
.iter()
|
||
.rev()
|
||
.filter_map(|frame| frame.active_rooting_oi().map(|oi| (oi, frame)))
|
||
.fold(None, |oeoi, (imm_oi, frame)| {
|
||
let eoi_next = oeoi
|
||
.map(|eoi| frame.env_cross_boundary_into(eoi))
|
||
.unwrap_or(EnvScopeKind::Visible(oi_ident));
|
||
|
||
asg.index(imm_oi, name, eoi_next);
|
||
Some(eoi_next)
|
||
});
|
||
|
||
oi_ident
|
||
}
|
||
}
|
||
|
||
/// Property of identifier scope within a given environment.
|
||
///
|
||
/// An _environment_ is the collection of identifiers associated with a
|
||
/// container object.
|
||
/// Environments stack,
|
||
/// such that an environment inherits the identifiers of its parent.
|
||
///
|
||
/// The _scope_ of an identifier is defined by what environments can "see"
|
||
/// that identifier.
|
||
/// For the purposes of TAME's analysis,
|
||
/// we care only about the global environment and shadowing.
|
||
///
|
||
/// The relationship between identifier scope and environment can be
|
||
/// visualized as a two-dimensional table with the environments forming
|
||
/// layers along the x-axes,
|
||
/// and scopes slicing those layers along the y-axies.
|
||
///
|
||
/// TODO: Example visualization.
|
||
///
|
||
/// Root and Global Environment
|
||
/// ===========================
|
||
/// Identifiers are pooled without any defined hierarchy at the root.
|
||
///
|
||
/// An identifier that is part of a pool must be unique.
|
||
/// Since there is no hierarchy,
|
||
/// the system should not suggest that shadowing is not permitted and
|
||
/// should insteam emphasize that such an identifier must be unique
|
||
/// globally.
|
||
///
|
||
/// An identifier's scope can be further refined to provide more useful
|
||
/// diagnostic messages by descending into the package in which it is
|
||
/// defined and evaluating scope relative to the package.
|
||
#[derive(Debug, PartialEq, Copy, Clone)]
|
||
pub(super) enum EnvScopeKind<T = ObjectIndex<Object>> {
|
||
/// This environment owns the identifier,
|
||
/// is descended from an environment that does,
|
||
/// or is a global pool of identifiers.
|
||
Visible(T),
|
||
|
||
/// Identifier in this environment is a shadow of a deeper environment.
|
||
///
|
||
/// An identifier is said to cast a shadow on environments higher in its
|
||
/// hierarchy.
|
||
/// Since shadowing is not permitted in TAME,
|
||
/// this can be used to present useful diagnostic information to the
|
||
/// user.
|
||
///
|
||
/// A shadow can be used to check for identifier conflicts,
|
||
/// but it cannot be used for lookup;
|
||
/// this environment should be filtered out of this identifier's
|
||
/// scope.
|
||
Shadow(T),
|
||
|
||
/// The identifier is not in scope.
|
||
Hidden(T),
|
||
}
|
||
|
||
impl<T> EnvScopeKind<T> {
|
||
pub fn into_inner(self) -> T {
|
||
use EnvScopeKind::*;
|
||
|
||
match self {
|
||
Shadow(x) | Visible(x) | Hidden(x) => x,
|
||
}
|
||
}
|
||
|
||
/// Whether this represents an identifier that is in scope.
|
||
pub fn in_scope(self) -> Option<Self> {
|
||
use EnvScopeKind::*;
|
||
|
||
match self {
|
||
Visible(_) => Some(self),
|
||
Shadow(_) | Hidden(_) => None,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T> AsRef<T> for EnvScopeKind<T> {
|
||
fn as_ref(&self) -> &T {
|
||
use EnvScopeKind::*;
|
||
|
||
match self {
|
||
Shadow(x) | Visible(x) | Hidden(x) => x,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T, U> Functor<T, U> for EnvScopeKind<T> {
|
||
type Target = EnvScopeKind<U>;
|
||
|
||
fn map(self, f: impl FnOnce(T) -> U) -> Self::Target {
|
||
use EnvScopeKind::*;
|
||
|
||
match self {
|
||
Shadow(x) => Shadow(f(x)),
|
||
Visible(x) => Visible(f(x)),
|
||
Hidden(x) => Hidden(f(x)),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T> From<EnvScopeKind<T>> for Span
|
||
where
|
||
T: Into<Span>,
|
||
{
|
||
fn from(kind: EnvScopeKind<T>) -> Self {
|
||
kind.into_inner().into()
|
||
}
|
||
}
|
||
|
||
impl AsMut<AirAggregateCtx> for AirAggregateCtx {
|
||
fn as_mut(&mut self) -> &mut AirAggregateCtx {
|
||
self
|
||
}
|
||
}
|
||
|
||
impl AsRef<Asg> for AirAggregateCtx {
|
||
fn as_ref(&self) -> &Asg {
|
||
match self {
|
||
Self(asg, _, _) => asg,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl AsMut<Asg> for AirAggregateCtx {
|
||
fn as_mut(&mut self) -> &mut Asg {
|
||
match self {
|
||
Self(asg, _, _) => asg,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl AsMut<AirStack> for AirAggregateCtx {
|
||
fn as_mut(&mut self) -> &mut AirStack {
|
||
match self {
|
||
Self(_, stack, _) => stack,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl From<AirAggregateCtx> for Asg {
|
||
fn from(ctx: AirAggregateCtx) -> Self {
|
||
match ctx {
|
||
AirAggregateCtx(asg, _, _) => asg,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl From<Asg> for AirAggregateCtx {
|
||
fn from(asg: Asg) -> Self {
|
||
Self(asg, Default::default(), None)
|
||
}
|
||
}
|
||
|
||
#[cfg(test)]
|
||
mod test;
|