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added documentation

This commit is contained in:
pca006132 2021-07-26 14:38:18 +08:00
parent bf31c48bba
commit 8d0856a58d
1 changed files with 12 additions and 0 deletions
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12
nac3core/src/typecheck/typedef/mod.rs
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@ -219,6 +219,13 @@ impl Unifier {
} }
(TVar { meta: Generic, id, range, .. }, _) => { (TVar { meta: Generic, id, range, .. }, _) => {
self.occur_check(a, b)?; self.occur_check(a, b)?;
// We check for the range of the type variable to see if unification is allowed.
// Note that although b may be compatible with a, we may have to constrain type
// variables in b to make sure that instantiations of b would always be compatible
// with a.
// The return value x of check_var_compatibility would be a new type that is
// guaranteed to be compatible with a under all possible instantiations. So we
// unify x with b to recursively apply the constrains, and then set a to x.
let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b); let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b);
self.unify(x, b)?; self.unify(x, b)?;
self.set_a_to_b(a, x); self.set_a_to_b(a, x);
@ -319,6 +326,8 @@ impl Unifier {
self.set_a_to_b(a, b); self.set_a_to_b(a, b);
} }
(TCall(calls1), TCall(calls2)) => { (TCall(calls1), TCall(calls2)) => {
// we do not unify individual calls, instead we defer until the unification wtih a
// function definition.
calls2.borrow_mut().extend_from_slice(&calls1.borrow()); calls2.borrow_mut().extend_from_slice(&calls1.borrow());
} }
(TCall(calls), TFunc(signature)) => { (TCall(calls), TFunc(signature)) => {
@ -330,6 +339,7 @@ impl Unifier {
.map(|v| v.name.clone()) .map(|v| v.name.clone())
.rev() .rev()
.collect(); .collect();
// we unify every calls to the function signature.
for c in calls.borrow().iter() { for c in calls.borrow().iter() {
let Call { posargs, kwargs, ret, fun } = c.as_ref(); let Call { posargs, kwargs, ret, fun } = c.as_ref();
let instantiated = self.instantiate_fun(b, signature); let instantiated = self.instantiate_fun(b, signature);
@ -341,6 +351,8 @@ impl Unifier {
} else { } else {
unreachable!(); unreachable!();
} }
// we check to make sure that all required arguments (those without default
// arguments) are provided, and do not provide the same argument twice.
let mut required = required.clone(); let mut required = required.clone();
let mut all_names: Vec<_> = let mut all_names: Vec<_> =
signature.args.iter().map(|v| (v.name.clone(), v.ty)).rev().collect(); signature.args.iter().map(|v| (v.name.clone(), v.ty)).rev().collect();