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finetuning some comments

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Folkert 2022-04-24 13:50:47 +02:00
parent dbae805071
commit cf89dd7f84
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1 changed files with 13 additions and 12 deletions
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25
compiler/can/src/def.rs
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@ -1953,10 +1953,12 @@ fn correct_mutual_recursive_type_alias<'a>(
// Don't try to instantiate the alias itself in its definition.
to_instantiate_bitvec.set(index, false);
// now we do something sneaky. In `can_instantiate_symbol` we want to be able to
// take a reference to an `Alias` in the `aliases` vec. That would not work if
// we also had a mutable reference to an alias in that vec. So we swap out the
// type.
// we run into a problem here where we want to modify an element in the aliases array,
// but also reference the other elements. The borrow checker, correctly, says no to that.
//
// So we get creative: we swap out the element we want to modify with a dummy. We can
// then freely modify the type we moved out, and the `to_instantiate_bitvec` mask
// prevents our dummy from being used.
let alias_region = aliases[index].region;
let mut alias_type = Type::EmptyRec;
@ -1981,13 +1983,12 @@ fn correct_mutual_recursive_type_alias<'a>(
// We can instantiate this alias in future iterations
to_instantiate_bitvec.set(index, true);
let alias = &mut aliases[index];
for lambda_set_var in new_lambda_sets {
alias
.lambda_set_variables
.push(LambdaSet(Type::Variable(lambda_set_var)));
}
// add any lambda sets that the instantiation created to the current alias
aliases[index].lambda_set_variables.extend(
new_lambda_sets
.iter()
.map(|var| LambdaSet(Type::Variable(*var))),
);
// Now mark the alias recursive, if it needs to be.
let rec = symbols_introduced[index];
@ -1998,7 +1999,7 @@ fn correct_mutual_recursive_type_alias<'a>(
let _made_recursive = make_tag_union_of_alias_recursive(
env,
rec,
alias,
&mut aliases[index],
vec![],
var_store,
&mut can_still_report_error,