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Make sure to apply "is-open" constraints at the very end of pattern constraining

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Closes #3298
This commit is contained in:
Ayaz Hafiz 2022-07-21 15:47:44 -04:00
parent 613606a67d
commit 13b0ce7ca0
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GPG key ID: 0E2A37416A25EF58
5 changed files with 85 additions and 62 deletions
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93
crates/compiler/constrain/src/expr.rs
View file

@ -735,6 +735,7 @@ pub fn constrain_expr(
let mut pattern_vars = Vec::with_capacity(branches.len());
let mut pattern_headers = SendMap::default();
let mut pattern_cons = Vec::with_capacity(branches.len() + 2);
let mut delayed_is_open_constraints = Vec::with_capacity(2);
let mut branch_cons = Vec::with_capacity(branches.len());
for (index, when_branch) in branches.iter().enumerate() {
@ -749,19 +750,24 @@ pub fn constrain_expr(
)
};
let (new_pattern_vars, new_pattern_headers, pattern_con, branch_con) =
constrain_when_branch_help(
constraints,
env,
region,
when_branch,
expected_pattern,
branch_expr_reason(
&expected,
HumanIndex::zero_based(index),
when_branch.value.region,
),
);
let (
new_pattern_vars,
new_pattern_headers,
pattern_con,
partial_delayed_is_open_constraints,
branch_con,
) = constrain_when_branch_help(
constraints,
env,
region,
when_branch,
expected_pattern,
branch_expr_reason(
&expected,
HumanIndex::zero_based(index),
when_branch.value.region,
),
);
pattern_vars.extend(new_pattern_vars);
@ -780,6 +786,7 @@ pub fn constrain_expr(
pattern_headers.extend(new_pattern_headers);
pattern_cons.push(pattern_con);
delayed_is_open_constraints.extend(partial_delayed_is_open_constraints);
branch_cons.push(branch_con);
}
@ -793,6 +800,11 @@ pub fn constrain_expr(
// The return type of each branch must equal the return type of
// the entire when-expression.
// Layer on the "is-open" constraints at the very end, after we know what the branch
// types are supposed to look like without open-ness.
let is_open_constr = constraints.and_constraint(delayed_is_open_constraints);
pattern_cons.push(is_open_constr);
// After solving the condition variable with what's expected from the branch patterns,
// check it against the condition expression.
//
@ -1804,6 +1816,7 @@ fn constrain_when_branch_help(
Vec<Variable>,
VecMap<Symbol, Loc<Type>>,
Constraint,
Vec<Constraint>,
Constraint,
) {
let ret_constraint = constrain_expr(
@ -1869,39 +1882,41 @@ fn constrain_when_branch_help(
}
}
let (pattern_constraints, body_constraints) = if let Some(loc_guard) = &when_branch.guard {
let guard_constraint = constrain_expr(
constraints,
env,
region,
&loc_guard.value,
Expected::ForReason(
Reason::WhenGuard,
Type::Variable(Variable::BOOL),
loc_guard.region,
),
);
let (pattern_constraints, delayed_is_open_constraints, body_constraints) =
if let Some(loc_guard) = &when_branch.guard {
let guard_constraint = constrain_expr(
constraints,
env,
region,
&loc_guard.value,
Expected::ForReason(
Reason::WhenGuard,
Type::Variable(Variable::BOOL),
loc_guard.region,
),
);
// must introduce the headers from the pattern before constraining the guard
state
.constraints
.append(&mut state.delayed_is_open_constraints);
let state_constraints = constraints.and_constraint(state.constraints);
let inner = constraints.let_constraint([], [], [], guard_constraint, ret_constraint);
// must introduce the headers from the pattern before constraining the guard
let delayed_is_open_constraints = state.delayed_is_open_constraints;
let state_constraints = constraints.and_constraint(state.constraints);
let inner = constraints.let_constraint([], [], [], guard_constraint, ret_constraint);
(state_constraints, inner)
} else {
state
.constraints
.append(&mut state.delayed_is_open_constraints);
let state_constraints = constraints.and_constraint(state.constraints);
(state_constraints, ret_constraint)
};
(state_constraints, delayed_is_open_constraints, inner)
} else {
let delayed_is_open_constraints = state.delayed_is_open_constraints;
let state_constraints = constraints.and_constraint(state.constraints);
(
state_constraints,
delayed_is_open_constraints,
ret_constraint,
)
};
(
state.vars,
state.headers,
pattern_constraints,
delayed_is_open_constraints,
body_constraints,
)
}