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|
use std::collections::HashMap;
use std::mem;
use ast::hir::{Binding, Pattern};
use ast::Literal;
use void::{ResultVoidExt, Void};
use crate::ast::hir::{Decl, Expr};
use crate::ast::{self, Ident};
use super::Visitor;
/// Strip all values with a unit type in positive (non-return) position
pub(crate) struct StripPositiveUnits {}
impl<'a, 'ast> Visitor<'a, 'ast, ast::Type<'ast>> for StripPositiveUnits {
type Error = Void;
fn pre_visit_expr(
&mut self,
expr: &mut Expr<'ast, ast::Type<'ast>>,
) -> Result<(), Self::Error> {
let mut extracted = vec![];
if let Expr::Call { args, .. } = expr {
// TODO(grfn): replace with drain_filter once it's stabilized
let mut i = 0;
while i != args.len() {
if args[i].type_() == &ast::Type::Unit {
let expr = args.remove(i);
if !matches!(expr, Expr::Literal(Literal::Unit, _)) {
extracted.push(expr)
};
} else {
i += 1
}
}
}
if !extracted.is_empty() {
let body = mem::replace(expr, Expr::Literal(Literal::Unit, ast::Type::Unit));
*expr = Expr::Let {
bindings: extracted
.into_iter()
.map(|expr| Binding {
pat: Pattern::Id(
Ident::from_str_unchecked("___discarded"),
expr.type_().clone(),
),
body: expr,
})
.collect(),
type_: body.type_().clone(),
body: Box::new(body),
};
}
Ok(())
}
fn post_visit_call(
&mut self,
_fun: &mut Expr<'ast, ast::Type<'ast>>,
_type_args: &mut HashMap<Ident<'ast>, ast::Type<'ast>>,
args: &mut Vec<Expr<'ast, ast::Type<'ast>>>,
) -> Result<(), Self::Error> {
args.retain(|arg| arg.type_() != &ast::Type::Unit);
Ok(())
}
fn visit_type(&mut self, type_: &mut ast::Type<'ast>) -> Result<(), Self::Error> {
if let ast::Type::Function(ft) = type_ {
ft.args.retain(|a| a != &ast::Type::Unit);
}
Ok(())
}
fn post_visit_fun_decl(
&mut self,
_name: &mut Ident<'ast>,
_type_args: &mut Vec<Ident>,
args: &mut Vec<(Ident, ast::Type<'ast>)>,
_body: &mut Box<Expr<ast::Type<'ast>>>,
_type_: &mut ast::Type<'ast>,
) -> Result<(), Self::Error> {
args.retain(|(_, ty)| ty != &ast::Type::Unit);
Ok(())
}
}
pub(crate) fn run_toplevel<'a>(toplevel: &mut Vec<Decl<'a, ast::Type<'a>>>) {
let mut pass = StripPositiveUnits {};
for decl in toplevel.iter_mut() {
pass.visit_decl(decl).void_unwrap();
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::parser::toplevel;
use crate::tc::typecheck_toplevel;
use pretty_assertions::assert_eq;
#[test]
fn unit_only_arg() {
let (_, program) = toplevel(
"ty f : fn () -> int
fn f _ = 1
ty main : fn -> int
fn main = f ()",
)
.unwrap();
let (_, expected) = toplevel(
"ty f : fn -> int
fn f = 1
ty main : fn -> int
fn main = f()",
)
.unwrap();
let expected = typecheck_toplevel(expected).unwrap();
let mut program = typecheck_toplevel(program).unwrap();
run_toplevel(&mut program);
assert_eq!(program, expected);
}
#[test]
fn unit_and_other_arg() {
let (_, program) = toplevel(
"ty f : fn (), int -> int
fn f _ x = x
ty main : fn -> int
fn main = f () 1",
)
.unwrap();
let (_, expected) = toplevel(
"ty f : fn int -> int
fn f x = x
ty main : fn -> int
fn main = f 1",
)
.unwrap();
let expected = typecheck_toplevel(expected).unwrap();
let mut program = typecheck_toplevel(program).unwrap();
run_toplevel(&mut program);
assert_eq!(program, expected);
}
#[test]
fn unit_expr_and_other_arg() {
let (_, program) = toplevel(
"ty f : fn (), int -> int
fn f _ x = x
ty g : fn int -> ()
fn g _ = ()
ty main : fn -> int
fn main = f (g 2) 1",
)
.unwrap();
let (_, expected) = toplevel(
"ty f : fn int -> int
fn f x = x
ty g : fn int -> ()
fn g _ = ()
ty main : fn -> int
fn main = let ___discarded = g 2 in f 1",
)
.unwrap();
assert_eq!(expected.len(), 6);
let expected = typecheck_toplevel(expected).unwrap();
let mut program = typecheck_toplevel(program).unwrap();
run_toplevel(&mut program);
assert_eq!(program, expected);
}
}
|
