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Internal compiler error when using generic items in array indexing in reassignments #5736

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ironcev opened this issue Mar 15, 2024 · 0 comments · Fixed by #5923
Closed

Internal compiler error when using generic items in array indexing in reassignments #5736

ironcev opened this issue Mar 15, 2024 · 0 comments · Fixed by #5923
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@ironcev
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bug Something isn't working compiler: frontend Everything to do with type checking, control flow analysis, and everything between parsing and IRgen compiler General compiler. Should eventually become more specific as the issue is triaged team:compiler Compiler Team

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ironcev commented Mar 15, 2024

This example will throw ICE:

script;

fn function<T>(_x: T) -> u64 {
    0
}

pub fn play<T>(x: T) {
   let mut array = [1, 2, 3];
   array[function(x)] = 0;
}

fn main() {
    play(0);
}

The ICE is:

fn function<T>(_x: T) -> u64 {
                   ^ Internal compiler error: Generic type cannot be resolved in IR.
@ironcev ironcev added bug Something isn't working compiler General compiler. Should eventually become more specific as the issue is triaged compiler: frontend Everything to do with type checking, control flow analysis, and everything between parsing and IRgen labels Mar 15, 2024
@ironcev ironcev self-assigned this Mar 15, 2024
@ironcev ironcev changed the title Internal compiler error when using generics in array indexing in reassignments Internal compiler error when using generic items in array indexing in reassignments Mar 15, 2024
@ironcev ironcev mentioned this issue Mar 15, 2024
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@ironcev ironcev mentioned this issue Apr 26, 2024
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IGI-111 pushed a commit that referenced this issue Apr 30, 2024
@ironcev
Dereferencing as reassignment target (#5923)
daee1c2 
## Description

This PR implements dereferencing in reassignment targets, as defined in
[references](https://github.com/FuelLabs/sway-rfcs/blob/ironcev/amend-references/files/0010-references.sw).
The overall effort related to references is tracked in
#5063.

Up to now, it was only possible to read the values references refer to.
This PR allows values to be written over `&mut` references. In other
words, any `*<expression that results in &mut>`is now an l-values and
can be used in left-hand sides (LHS) of assignments. In most of the
cases, the `<expression>` will very likely be just a reference variable,
but any expression that results in `&mut` is allowed and supported.
E.g.;

```Sway
*mut_ref_to_u64 = 42;

*if condition { &mut x } else { &mut y } = 42;

*max_mut(&mut x, &mut y) = 42;
```

Additionally, the PR:
- fixes #5736 by properly replacing decls in reassignment LHSs.
- fixes #5737 by properly substituting types in reassignment LHSs.
- fixes #5920 by properly connecting expressions in array indices to the
DCA graph.
- fixes #5922 by type-cheking the array indices in reassignment LHSs and
forcing them to be `u64`.
- improves misplaced and misleading error messages when assigning to
constants and other items (see demo below).
- improves error message when assigning to immutable variables by
pointing to variable declaration.
- improves error message when expression cannot be assigned to by
pointing to the problematic part of the expression. Since Sway is more
restrictive here then Rust, the restrictions, without being explained,
could cause confusion. That's why special attention was given to point
to the exact issue and explain what is actually supported in Sway (see
demo below).
- reduces number of expected warnings in references E2E tests that were
previously set high because of DCA issues that are fixed in the
meantime.

The PR also brings additional analysis and checks to IR optimizations.
Among other things, it explicitly points out the cases in which a
potential usage of a symbol cannot be deterministically confirmed or
denied. In this PR properly reacting for such cases is done in some
optimizations. Rolling it out fully will be done in a follow up PR
#5924. More advanced escape analysis will be done later on, as a part of
allocating values on the heap in case of referencing.

This PR implements only dereferencing in LHS. Support for referenced
elements in the element based access (without dereferencing) will be
done in a separate step as an ongoing work on implementing #5063.

Closes #5736, #5737, #5920, #5922.

## Demo

Before:
![Assignment to constant -
Before](https://github.com/FuelLabs/sway/assets/4142833/e6b29d31-8e29-4ffa-acfe-a844ac50887b)

![Assignment to decl -
Before](https://github.com/FuelLabs/sway/assets/4142833/ef5f025e-3dcc-4cb0-b52f-d735e2ee451e)

After:
![Assignment to constant -
After](https://github.com/FuelLabs/sway/assets/4142833/f3dfdbd9-2123-4a96-98a7-b3c7a3f3e7f9)

![Assignment to decl -
After](https://github.com/FuelLabs/sway/assets/4142833/ae765d61-41b2-478c-96c0-d476604deec6)

Expression cannot be assigned to:

![Expression cannot be assigned
to](https://github.com/FuelLabs/sway/assets/4142833/384d0bb7-34a1-446a-acd5-6c8f66dc4ed5)

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [ ] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.
@IGI-111 IGI-111 added the team:compiler Compiler Team label Feb 10, 2025
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bug Something isn't working compiler: frontend Everything to do with type checking, control flow analysis, and everything between parsing and IRgen compiler General compiler. Should eventually become more specific as the issue is triaged team:compiler Compiler Team
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Dereferencing as reassignment target FuelLabs/sway
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