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type inference for pattern guards

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This commit is contained in:
Folkert 2020-03-21 00:39:52 +01:00
parent 655dc32098
commit 920928399a
9 changed files with 230 additions and 57 deletions
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47
compiler/constrain/src/expr.rs
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@ -7,7 +7,7 @@ use roc_can::def::{Declaration, Def};
use roc_can::expected::Expected::{self, *};
use roc_can::expected::PExpected;
use roc_can::expr::Expr::{self, *};
use roc_can::expr::Field;
use roc_can::expr::{Field, WhenBranch};
use roc_can::pattern::Pattern;
use roc_collections::all::{ImMap, SendMap};
use roc_module::ident::Lowercase;
@ -451,12 +451,11 @@ pub fn constrain_expr(
let ast_con = Eq(Type::Variable(*expr_var), expected.clone(), region);
constraints.push(ast_con);
for (index, (loc_when_pattern, loc_expr)) in branches.iter().enumerate() {
for (index, when_branch) in branches.iter().enumerate() {
let branch_con = constrain_when_branch(
env,
region,
&loc_when_pattern,
loc_expr,
when_branch,
PExpected::ForReason(
PReason::WhenMatch { index },
cond_type.clone(),
@ -478,12 +477,11 @@ pub fn constrain_expr(
let branch_type = Variable(*expr_var);
let mut branch_cons = Vec::with_capacity(branches.len());
for (index, (loc_when_pattern, loc_expr)) in branches.iter().enumerate() {
for (index, when_branch) in branches.iter().enumerate() {
let branch_con = constrain_when_branch(
env,
region,
&loc_when_pattern,
loc_expr,
when_branch,
PExpected::ForReason(
PReason::WhenMatch { index },
cond_type.clone(),
@ -662,12 +660,11 @@ pub fn constrain_expr(
fn constrain_when_branch(
env: &Env,
region: Region,
loc_pattern: &Located<Pattern>,
loc_expr: &Located<Expr>,
when_branch: &WhenBranch,
pattern_expected: PExpected<Type>,
expr_expected: Expected<Type>,
) -> Constraint {
let ret_constraint = constrain_expr(env, region, &loc_expr.value, expr_expected);
let ret_constraint = constrain_expr(env, region, &when_branch.value.value, expr_expected);
let mut state = PatternState {
headers: SendMap::default(),
@ -675,12 +672,30 @@ fn constrain_when_branch(
constraints: Vec::with_capacity(1),
};
constrain_pattern(
&loc_pattern.value,
loc_pattern.region,
pattern_expected,
&mut state,
);
// TODO ensure this is correct
// TODO investigate for error messages, is it better to unify all branches with a variable,
// then unify that variable with the expectation?
for loc_pattern in &when_branch.patterns {
constrain_pattern(
&loc_pattern.value,
loc_pattern.region,
pattern_expected.clone(),
&mut state,
);
}
if let Some(loc_guard) = &when_branch.guard {
state.constraints.push(constrain_expr(
env,
region,
&when_branch.value.value,
Expected::ForReason(
Reason::WhenGuard,
Type::Variable(Variable::BOOL),
loc_guard.region,
),
));
};
Constraint::Let(Box::new(LetConstraint {
rigid_vars: Vec::new(),