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make runtime errors for invalid patterns

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Folkert 2020-03-31 01:47:14 +02:00
parent 2586fde6af
commit db3ffc6dab
3 changed files with 26 additions and 12 deletions
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34
compiler/mono/src/expr.rs
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@ -340,31 +340,43 @@ fn pattern_to_when<'a>(
// for underscore we generate a dummy Symbol
(env.fresh_symbol(), body)
}
Shadowed(_, _) | UnsupportedPattern(_) => {
// create the runtime error here, instead of delegating to When.
// UnsupportedPattern should then never occcur in When
panic!("TODO generate runtime error here");
Shadowed(region, loc_ident) => {
let error = roc_problem::can::RuntimeError::Shadowing {
original_region: *region,
shadow: loc_ident.clone(),
};
(env.fresh_symbol(), Located::at_zero(RuntimeError(error)))
}
AppliedTag {..} | RecordDestructure {..} => {
UnsupportedPattern(region) => {
// create the runtime error here, instead of delegating to When.
// UnsupportedPattern should then never occcur in When
let error = roc_problem::can::RuntimeError::UnsupportedPattern(*region);
(env.fresh_symbol(), Located::at_zero(RuntimeError(error)))
}
AppliedTag { .. } | RecordDestructure { .. } => {
let symbol = env.fresh_symbol();
let wrapped_body = When {
cond_var: pattern_var,
expr_var: body_var,
loc_cond: Box::new(Located::at_zero(Var(symbol))),
branches: vec![WhenBranch{ patterns: vec![pattern], value: body, guard: None }],
branches: vec![WhenBranch {
patterns: vec![pattern],
value: body,
guard: None,
}],
};
(symbol, Located::at_zero(wrapped_body))
}
// These patters are refutable, and thus should never occur outside a `when` expression
IntLiteral(_) | NumLiteral(_,_) | FloatLiteral(_) | StrLiteral(_) => {
IntLiteral(_) | NumLiteral(_, _) | FloatLiteral(_) | StrLiteral(_) => {
// These patters are refutable, and thus should never occur outside a `when` expression
// They should have been replaced with `UnsupportedPattern` during canonicalization
unreachable!("refutable pattern {:?} where irrefutable pattern is expected. This should never happen!", pattern.value)
}
}
}
@ -1019,7 +1031,7 @@ fn from_can_when<'a>(
if branches.is_empty() {
// A when-expression with no branches is a runtime error.
// We can't know what to return!
panic!("TODO compile a 0-branch when-expression to a RuntimeError");
Expr::RuntimeError("Hit a 0-branch when expression")
} else if branches.len() == 1 && branches[0].patterns.len() == 1 && branches[0].guard.is_none()
{
let first = branches.remove(0);