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//! Lower
//!
use intern::{self, intern, InternedString};
use normalize::NormResult;
use normalize::norm_util::{self, Symbols};
use grammar::consts::*;
use grammar::pattern::{Pattern, PatternKind};
use grammar::parse_tree as pt;
use grammar::parse_tree::{InternToken, NonterminalString, TerminalString, read_algorithm};
use grammar::repr as r;
use session::Session;
use collections::{map, Map};
pub fn lower(session: &Session, grammar: pt::Grammar, types: r::Types) -> NormResult<r::Grammar> {
let state = LowerState::new(session, types, &grammar);
state.lower(grammar)
}
struct LowerState<'s> {
session: &'s Session,
prefix: String,
action_fn_defns: Vec<r::ActionFnDefn>,
nonterminals: Map<NonterminalString, r::NonterminalData>,
conversions: Vec<(TerminalString, Pattern<r::TypeRepr>)>,
intern_token: Option<InternToken>,
types: r::Types,
uses_error_recovery: bool,
}
impl<'s> LowerState<'s> {
fn new(session: &'s Session, types: r::Types, grammar: &pt::Grammar) -> Self {
LowerState {
session: session,
prefix: grammar.prefix.clone(),
action_fn_defns: vec![],
nonterminals: map(),
conversions: vec![],
types: types,
intern_token: None,
uses_error_recovery: false,
}
}
fn lower(mut self, grammar: pt::Grammar) -> NormResult<r::Grammar> {
let start_symbols = self.synthesize_start_symbols(&grammar);
let mut uses = vec![];
let mut token_span = None;
for item in grammar.items {
match item {
pt::GrammarItem::Use(data) => {
uses.push(data);
}
pt::GrammarItem::InternToken(data) => {
token_span = Some(grammar.span);
let span = grammar.span;
let input_str = r::TypeRepr::Ref {
lifetime: Some(intern(INPUT_LIFETIME)),
mutable: false,
referent: Box::new(r::TypeRepr::Nominal(r::NominalTypeRepr {
path: r::Path::str(),
types: vec![],
})),
};
self.conversions.extend(data.literals
.iter()
.enumerate()
.map(|(index, &literal)| {
let pattern = Pattern {
span: span,
kind: PatternKind::Tuple(vec![
Pattern {
span: span,
kind: PatternKind::Usize(index),
},
Pattern {
span: span,
kind: PatternKind::Choose(input_str.clone())
}
]),
};
(TerminalString::Literal(literal), pattern)
}));
self.intern_token = Some(data);
}
pt::GrammarItem::ExternToken(data) => {
if let Some(enum_token) = data.enum_token {
token_span = Some(enum_token.type_span);
self.conversions.extend(enum_token.conversions
.iter()
.map(|conversion| {
(conversion.from,
conversion.to.map(&mut |t| {
t.type_repr()
}))
}));
}
}
pt::GrammarItem::Nonterminal(nt) => {
let nt_name = nt.name;
let productions: Vec<_> = nt.alternatives
.into_iter()
.map(|alt| {
let nt_type = self.types
.nonterminal_type(nt_name)
.clone();
let symbols = self.symbols(&alt.expr.symbols);
let action = self.action_kind(nt_type,
&alt.expr,
&symbols,
alt.action);
r::Production {
nonterminal: nt_name,
span: alt.span,
symbols: symbols,
action: action,
}
})
.collect();
self.nonterminals.insert(nt_name,
r::NonterminalData {
name: nt_name,
annotations: nt.annotations,
span: nt.span,
productions: productions,
});
}
}
}
let parameters = grammar.parameters
.iter()
.map(|p| {
r::Parameter {
name: p.name,
ty: p.ty.type_repr(),
}
})
.collect();
let mut algorithm = r::Algorithm::default();
// FIXME Error recovery only works for parse tables so temporarily only generate parse tables for
// testing
if self.session.unit_test && !self.uses_error_recovery {
algorithm.codegen = r::LrCodeGeneration::TestAll;
}
read_algorithm(&grammar.annotations, &mut algorithm);
let mut all_terminals: Vec<_> = self.conversions
.iter()
.map(|c| c.0)
.chain(Some(TerminalString::Error))
.collect();
all_terminals.sort();
let terminal_bits: Map<_, _> = all_terminals.iter()
.cloned()
.zip(0..)
.collect();
Ok(r::Grammar {
prefix: self.prefix,
start_nonterminals: start_symbols,
uses: uses,
action_fn_defns: self.action_fn_defns,
nonterminals: self.nonterminals,
conversions: self.conversions.into_iter().collect(),
types: self.types,
token_span: token_span.unwrap(),
type_parameters: grammar.type_parameters,
parameters: parameters,
where_clauses: grammar.where_clauses,
algorithm: algorithm,
intern_token: self.intern_token,
terminals: r::TerminalSet {
all: all_terminals,
bits: terminal_bits,
},
})
}
fn synthesize_start_symbols(&mut self,
grammar: &pt::Grammar)
-> Map<NonterminalString, NonterminalString> {
grammar.items
.iter()
.filter_map(|item| item.as_nonterminal())
.filter(|nt| nt.public)
.map(|nt| {
// create a synthetic symbol `__Foo` for each public symbol `Foo`
// with a rule like:
//
// __Foo = Foo;
let fake_name = pt::NonterminalString(intern(&format!("{}{}",
self.prefix,
nt.name)));
let nt_type = self.types.nonterminal_type(nt.name).clone();
self.types.add_type(fake_name, nt_type.clone());
let expr = pt::ExprSymbol {
symbols: vec![pt::Symbol::new(nt.span,
pt::SymbolKind::Nonterminal(fake_name))],
};
let symbols = vec![r::Symbol::Nonterminal(nt.name)];
let action_fn = self.action_fn(nt_type, false, &expr, &symbols, None);
let production = r::Production {
nonterminal: fake_name,
symbols: symbols,
action: action_fn,
span: nt.span,
};
self.nonterminals.insert(fake_name,
r::NonterminalData {
name: fake_name,
annotations: vec![],
span: nt.span,
productions: vec![production],
});
(nt.name, fake_name)
})
.collect()
}
fn action_kind(&mut self,
nt_type: r::TypeRepr,
expr: &pt::ExprSymbol,
symbols: &[r::Symbol],
action: Option<pt::ActionKind>)
-> r::ActionFn {
match action {
Some(pt::ActionKind::Lookahead) => self.lookahead_action_fn(),
Some(pt::ActionKind::Lookbehind) => self.lookbehind_action_fn(),
Some(pt::ActionKind::User(string)) => {
self.action_fn(nt_type, false, &expr, &symbols, Some(string))
}
Some(pt::ActionKind::Fallible(string)) => {
self.action_fn(nt_type, true, &expr, &symbols, Some(string))
}
None => self.action_fn(nt_type, false, &expr, &symbols, None),
}
}
fn lookahead_action_fn(&mut self) -> r::ActionFn {
let action_fn_defn = r::ActionFnDefn {
fallible: false,
ret_type: self.types.terminal_loc_type(),
kind: r::ActionFnDefnKind::Lookaround(r::LookaroundActionFnDefn::Lookahead),
};
self.add_action_fn(action_fn_defn)
}
fn lookbehind_action_fn(&mut self) -> r::ActionFn {
let action_fn_defn = r::ActionFnDefn {
fallible: false,
ret_type: self.types.terminal_loc_type(),
kind: r::ActionFnDefnKind::Lookaround(r::LookaroundActionFnDefn::Lookbehind),
};
self.add_action_fn(action_fn_defn)
}
fn action_fn(&mut self,
nt_type: r::TypeRepr,
fallible: bool,
expr: &pt::ExprSymbol,
symbols: &[r::Symbol],
action: Option<String>)
-> r::ActionFn {
let action = match action {
Some(s) => s,
None => {
// If the user declared a type `()`, or we inferred
// it, then there is only one possible action that
// will type-check (`()`), so supply that. Otherwise,
// default is to include all selected items.
if nt_type.is_unit() {
format!("()")
} else {
format!("(<>)")
}
}
};
// Note that the action fn takes ALL of the symbols in `expr`
// as arguments, and some of them are simply dropped based on
// the user's selections.
// The set of argument types is thus the type of all symbols:
let arg_types: Vec<r::TypeRepr> = symbols.iter()
.map(|s| s.ty(&self.types))
.cloned()
.collect();
let action_fn_defn = match norm_util::analyze_expr(expr) {
Symbols::Named(names) => {
// if there are named symbols, we want to give the
// arguments the names that the user gave them:
let arg_patterns = patterns(names.iter().map(|&(index, name, _)| (index, name)),
symbols.len());
r::ActionFnDefn {
fallible: fallible,
ret_type: nt_type,
kind: r::ActionFnDefnKind::User(r::UserActionFnDefn {
arg_patterns: arg_patterns,
arg_types: arg_types,
code: action,
}),
}
}
Symbols::Anon(indices) => {
let names: Vec<_> = (0..indices.len()).map(|i| self.fresh_name(i)).collect();
let arg_patterns = patterns(indices.iter()
.map(|&(index, _)| index)
.zip(names.iter().cloned()),
symbols.len());
let name_str = intern::read(|interner| {
let name_strs: Vec<_> = names.iter().map(|&n| interner.data(n)).collect();
name_strs.join(", ")
});
let action = action.replace("<>", &name_str);
r::ActionFnDefn {
fallible: fallible,
ret_type: nt_type,
kind: r::ActionFnDefnKind::User(r::UserActionFnDefn {
arg_patterns: arg_patterns,
arg_types: arg_types,
code: action,
}),
}
}
};
self.add_action_fn(action_fn_defn)
}
fn add_action_fn(&mut self, action_fn_defn: r::ActionFnDefn) -> r::ActionFn {
let index = r::ActionFn::new(self.action_fn_defns.len());
self.action_fn_defns.push(action_fn_defn);
index
}
fn symbols(&mut self, symbols: &[pt::Symbol]) -> Vec<r::Symbol> {
symbols.iter().map(|sym| self.symbol(sym)).collect()
}
fn symbol(&mut self, symbol: &pt::Symbol) -> r::Symbol {
match symbol.kind {
pt::SymbolKind::Terminal(id) => r::Symbol::Terminal(id),
pt::SymbolKind::Nonterminal(id) => r::Symbol::Nonterminal(id),
pt::SymbolKind::Choose(ref s) | pt::SymbolKind::Name(_, ref s) => self.symbol(s),
pt::SymbolKind::Error => {
self.uses_error_recovery = true;
r::Symbol::Terminal(TerminalString::Error)
}
pt::SymbolKind::Macro(..) |
pt::SymbolKind::Repeat(..) |
pt::SymbolKind::Expr(..) |
pt::SymbolKind::AmbiguousId(_) |
pt::SymbolKind::Lookahead |
pt::SymbolKind::Lookbehind => {
unreachable!("symbol `{}` should have been normalized away by now",
symbol)
}
}
}
fn fresh_name(&self, i: usize) -> InternedString {
intern(&format!("{}{}", self.prefix, i))
}
}
fn patterns<I>(mut chosen: I, num_args: usize) -> Vec<InternedString>
where I: Iterator<Item = (usize, InternedString)>
{
let blank = intern("_");
let mut next_chosen = chosen.next();
let result = (0..num_args)
.map(|index| {
match next_chosen {
Some((chosen_index, chosen_name)) if chosen_index == index => {
next_chosen = chosen.next();
chosen_name
}
_ => blank,
}
})
.collect();
debug_assert!(next_chosen.is_none());
result
}