Constant evaluation

[Y-Nak]

This PR adds some features and fixes some ICE related to constant evaluation.

Features

1. Support local constant

Example:

contract Foo:
    pub fn bar():
        const LOCAL_CONST: i32 = 1

2. Support constant expression

Example:

const GLOBAL: i32 = 8

contract Foo:
    pub fn bar():
        const LOCAL: i32 = GLOBAL * 8

3. Support constant generics expression

Example:

const GLOBAL: u256= 8
const USE_GLOBAL: bool = false
type MY_ARRAY = Array<i32, { GLOBAL / 4 }>

contract Foo:
    pub fn bar():
        let my_array: Array<i32, { GLOBAL if USE_GLOBAL else 4 }>

Bug fixes

Fix ICE when constant type is a mismatch

Example:

const GLOBAL: i32 = "FOO"

contract Foo:
    pub fn bar():
        let FOO: i32 = GLOBAL

Fix ICE when assigning value to constant twice

Example:

const BAR: i32 = 1

contract FOO:
    pub fn bar():
        BAR = 10

TODO

I opened a follow-up issue here

[codecov-commenter]

Codecov Report

Merging #649 (64c7dfd) into master (3ec1711) will decrease coverage by 0.99%.
The diff coverage is 72.25%.

@@            Coverage Diff             @@
##           master     #649      +/-   ##
==========================================
- Coverage   86.80%   85.81%   -1.00%     
==========================================
  Files          96       97       +1     
  Lines        8627     9075     +448     
==========================================
+ Hits         7489     7788     +299     
- Misses       1138     1287     +149     

Impacted Files	Coverage Δ
crates/analyzer/src/db.rs	100.00% <ø> (ø)
crates/parser/src/ast.rs	88.95% <0.00%> (+0.12%)	⬆️
crates/analyzer/src/namespace/types.rs	71.18% <12.50%> (-5.97%)	⬇️
crates/analyzer/src/context.rs	65.21% <16.00%> (-14.79%)	⬇️
crates/lowering/src/ast_utils.rs	83.50% <20.00%> (-0.82%)	⬇️
crates/analyzer/src/errors.rs	92.85% <50.00%> (-7.15%)	⬇️
crates/analyzer/src/db/queries/module.rs	79.03% <51.35%> (-6.97%)	⬇️
crates/analyzer/src/namespace/scopes.rs	72.34% <66.66%> (-4.29%)	⬇️
crates/parser/src/grammar/functions.rs	90.39% <76.92%> (-1.27%)	⬇️
crates/analyzer/src/traversal/expressions.rs	81.58% <79.45%> (-0.63%)	⬇️
... and 21 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3ec1711...64c7dfd. Read the comment docs.

[g-r-a-n-t]

great work!

[Y-Nak]

Fixed an invalid example in news fragments.

[cburgdorf]

Just a nitpick but next time it would be better to create another file 649.bugfix.md because our changelog generator picks up these file name keywords to group the items accordingly. No big deal though, we can always apply changes to the changelog by hand.

[Y-Nak]

Oh, Ok. I understand.