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remember recursion variable when making alias recursive

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Folkert 2022-03-16 14:52:34 +01:00
parent 1dacf29879
commit 7f63e09272
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GPG key ID: 1F17F6FFD112B97C
1 changed files with 34 additions and 10 deletions
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44
compiler/can/src/def.rs
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@ -1748,7 +1748,7 @@ fn make_tag_union_of_alias_recursive<'a>(
.map(|l| (l.value.0.clone(), Type::Variable(l.value.1)))
.collect::<Vec<_>>();
make_tag_union_recursive_help(
let made_recursive = make_tag_union_recursive_help(
env,
Loc::at(alias.header_region(), (alias_name, &alias_args)),
alias.region,
@ -1756,7 +1756,24 @@ fn make_tag_union_of_alias_recursive<'a>(
&mut alias.typ,
var_store,
can_report_error,
)
);
match made_recursive {
MakeTagUnionRecursive::Cyclic => Ok(()),
MakeTagUnionRecursive::MadeRecursive { recursion_variable } => {
alias.recursion_variables.clear();
alias.recursion_variables.insert(recursion_variable);
Ok(())
}
MakeTagUnionRecursive::InvalidRecursion => Err(()),
}
}
enum MakeTagUnionRecursive {
Cyclic,
MadeRecursive { recursion_variable: Variable },
InvalidRecursion,
}
/// Attempt to make a tag union recursive at the position of `recursive_alias`; for example,
@ -1788,7 +1805,9 @@ fn make_tag_union_recursive_help<'a>(
typ: &mut Type,
var_store: &mut VarStore,
can_report_error: &mut bool,
) -> Result<(), ()> {
) -> MakeTagUnionRecursive {
use MakeTagUnionRecursive::*;
let Loc {
value: (symbol, args),
region: alias_region,
@ -1796,15 +1815,17 @@ fn make_tag_union_recursive_help<'a>(
let vars = args.iter().map(|(_, t)| t.clone()).collect::<Vec<_>>();
match typ {
Type::TagUnion(tags, ext) => {
let rec_var = var_store.fresh();
let mut pending_typ = Type::RecursiveTagUnion(rec_var, tags.to_vec(), ext.clone());
let recursion_variable = var_store.fresh();
let mut pending_typ =
Type::RecursiveTagUnion(recursion_variable, tags.to_vec(), ext.clone());
let substitution_result =
pending_typ.substitute_alias(symbol, &vars, &Type::Variable(rec_var));
pending_typ.substitute_alias(symbol, &vars, &Type::Variable(recursion_variable));
match substitution_result {
Ok(()) => {
// We can substitute the alias presence for the variable exactly.
*typ = pending_typ;
Ok(())
MadeRecursive { recursion_variable }
}
Err(differing_recursion_region) => {
env.problems.push(Problem::NestedDatatype {
@ -1812,11 +1833,14 @@ fn make_tag_union_recursive_help<'a>(
def_region: alias_region,
differing_recursion_region,
});
Err(())
InvalidRecursion
}
}
}
Type::RecursiveTagUnion(_, _, _) => Ok(()),
Type::RecursiveTagUnion(recursion_variable, _, _) => MadeRecursive {
recursion_variable: *recursion_variable,
},
Type::Alias {
actual,
type_arguments,
@ -1834,7 +1858,7 @@ fn make_tag_union_recursive_help<'a>(
mark_cyclic_alias(env, typ, symbol, region, others, *can_report_error);
*can_report_error = false;
Ok(())
Cyclic
}
}
}