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change constraints gen to give better errors

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This commit is contained in:
Folkert 2020-11-15 02:06:34 +01:00
parent 00978994bf
commit 197abd8553
1 changed files with 21 additions and 20 deletions
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41
compiler/constrain/src/expr.rs
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@ -431,6 +431,7 @@ pub fn constrain_expr(
match expected {
FromAnnotation(name, arity, _, tipe) => {
let num_branches = branches.len() + 1;
for (index, (loc_cond, loc_body)) in branches.iter().enumerate() {
let cond_con = constrain_expr(
env,
@ -448,7 +449,7 @@ pub fn constrain_expr(
arity,
AnnotationSource::TypedIfBranch {
index: Index::zero_based(index),
num_branches: branches.len(),
num_branches,
},
tipe.clone(),
),
@ -467,7 +468,7 @@ pub fn constrain_expr(
arity,
AnnotationSource::TypedIfBranch {
index: Index::zero_based(branches.len()),
num_branches: branches.len(),
num_branches,
},
tipe.clone(),
),
@ -558,15 +559,12 @@ pub fn constrain_expr(
constraints.push(expr_con);
match &expected {
FromAnnotation(name, arity, _, typ) => {
// record the type of the whole expression in the AST
let ast_con = Eq(
Type::Variable(*expr_var),
expected.clone(),
Category::Storage(std::file!(), std::line!()),
region,
);
constraints.push(ast_con);
FromAnnotation(name, arity, _, _typ) => {
// NOTE deviation from elm.
//
// in elm, `_typ` is used, but because we have this `expr_var` too
// and need to constrain it, this is what works and gives better error messages
let typ = Type::Variable(*expr_var);
for (index, when_branch) in branches.iter().enumerate() {
let pattern_region =
@ -595,6 +593,10 @@ pub fn constrain_expr(
constraints.push(branch_con);
}
constraints.push(Eq(typ, expected, Category::When, region));
return exists(vec![cond_var, *expr_var], And(constraints));
}
_ => {
@ -1124,7 +1126,6 @@ fn constrain_def(env: &Env, def: &Def, body_con: Constraint) -> Constraint {
// NOTE if we ever have problems with the closure, the ignored `_closure_type`
// is probably a good place to start the investigation!
let expected = annotation_expected;
let region = def.loc_expr.region;
let loc_body_expr = &**loc_body;
@ -1200,12 +1201,15 @@ fn constrain_def(env: &Env, def: &Def, body_con: Constraint) -> Constraint {
&mut vars,
);
let fn_type = Type::Function(
pattern_types,
Box::new(Type::Variable(closure_var)),
Box::new(ret_type.clone()),
let body_type = FromAnnotation(
def.loc_pattern.clone(),
arguments.len(),
AnnotationSource::TypedBody {
region: annotation.region,
},
ret_type.clone(),
);
let body_type = NoExpectation(ret_type.clone());
let ret_constraint =
constrain_expr(env, loc_body_expr.region, &loc_body_expr.value, body_type);
@ -1222,9 +1226,6 @@ fn constrain_def(env: &Env, def: &Def, body_con: Constraint) -> Constraint {
defs_constraint,
ret_constraint,
})),
// "the closure's type is equal to expected type"
Eq(fn_type, expected, Category::Lambda, region),
// Store type into AST vars. We use Store so errors aren't reported twice
Store(signature.clone(), *fn_var, std::file!(), std::line!()),
Store(signature, expr_var, std::file!(), std::line!()),
Store(ret_type, ret_var, std::file!(), std::line!()),