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use super::{extra_tokens_diag, Parser};
use crate::common::Span;
use crate::diagnostics::Diagnostic;
use crate::grammar::*;
use crate::scanner::types::Token;
use crate::utils::{hash, PeekIter};
use std::collections::HashMap;
use std::rc::Rc;
pub fn parse(input: Vec<Token>) -> (Rc<ExprPat>, Vec<Diagnostic>) {
let mut parser = ExpressionPatternParser::new(input);
(parser.parse(), parser.diagnostics)
}
pub struct ExpressionPatternParser {
_input: PeekIter<Token>,
diagnostics: Vec<Diagnostic>,
seen: HashMap<u64, Rc<ExprPat>>,
}
impl Parser<Rc<ExprPat>> for ExpressionPatternParser {
type Expr = ExprPat;
fn new(input: Vec<Token>) -> Self {
Self {
_input: PeekIter::new(input.into_iter()),
diagnostics: vec![],
seen: HashMap::new(),
}
}
fn input(&mut self) -> &mut PeekIter<Token> {
&mut self._input
}
fn push_diag(&mut self, diagnostic: Diagnostic) {
self.diagnostics.push(diagnostic);
}
fn parse(&mut self) -> Rc<ExprPat> {
let parsed = self.expr();
if !self.done() {
let extra_tokens_diag = extra_tokens_diag(self.input());
self.push_diag(extra_tokens_diag);
}
parsed
}
fn parse_float(&mut self, f: f64, _span: Span) -> Self::Expr {
Self::Expr::Const(f)
}
fn parse_variable(&mut self, name: String, span: Span) -> Self::Expr {
self.push_diag(
Diagnostic::span_err(
span,
"Variables cannot be used in an expression pattern",
Some("unexpected variable".into()),
)
.with_help(format!(
r##"consider using "${name}", "#{name}", or "_{name}" as a pattern"##,
name = name,
)),
);
Self::Expr::VarPat(name)
}
fn parse_var_pattern(&mut self, name: String, _span: Span) -> Self::Expr {
Self::Expr::VarPat(name)
}
fn parse_const_pattern(&mut self, name: String, _span: Span) -> Self::Expr {
Self::Expr::ConstPat(name)
}
fn parse_any_pattern(&mut self, name: String, _span: Span) -> Self::Expr {
Self::Expr::AnyPat(name)
}
fn finish_expr(&mut self, expr: Self::Expr) -> Rc<Self::Expr> {
let p = self
.seen
.entry(hash(&expr))
.or_insert_with(|| Rc::new(expr));
Rc::clone(p)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::scan;
parser_tests! {
parse_expression_pattern
pattern: "$a"
pattern_in_op_left: "$a + 1"
pattern_in_op_right: "1 + $a"
}
#[test]
fn common_subexpression_elimination() {
let program = "$v * #c + $v * #c";
let tokens = scan(program).tokens;
let (parsed, _) = parse(tokens);
let (l, r) = match (*parsed).clone() {
ExprPat::BinaryExpr(BinaryExpr { lhs, rhs, .. }) => (lhs, rhs),
_ => unreachable!(),
};
assert!(std::ptr::eq(l.as_ref(), r.as_ref()));
let (ll, lr, rl, rr) = match (l.as_ref(), r.as_ref()) {
(
ExprPat::BinaryExpr(BinaryExpr {
lhs: ll, rhs: lr, ..
}),
ExprPat::BinaryExpr(BinaryExpr {
lhs: rl, rhs: rr, ..
}),
) => (ll, lr, rl, rr),
_ => unreachable!(),
};
assert!(std::ptr::eq(ll.as_ref(), rl.as_ref()));
assert!(std::ptr::eq(lr.as_ref(), rr.as_ref()));
}
}