Store usage in db.

[ilyalesokhin-starkware]

This change is 

[orizi]

Reviewed 2 of 5 files at r1, all commit messages.
Reviewable status: 2 of 5 files reviewed, 3 unresolved discussions (waiting on @ilyalesokhin-starkware)

---

crates/cairo-lang-lowering/src/lower/mod.rs line 1390 at r1 (raw file):

    };

    let usage = ctx.db.function_expr_usage(ctx.semantic_function_id, loop_expr_id).unwrap();

how do we know this unwrap won't cause a panic?
same below.

---

crates/cairo-lang-semantic/src/db.rs line 1483 at r1 (raw file):

    fn file_semantic_diagnostics(&self, file_id: FileId) -> Maybe<Diagnostics<SemanticDiagnostic>>;

    // usage.

Suggestion:

    // Usage.

---

crates/cairo-lang-semantic/src/db.rs line 1486 at r1 (raw file):

    // ========
    #[salsa::invoke(usage::function_expr_usage)]
    fn function_expr_usage(

doc

[ilyalesokhin-starkware]

crates/cairo-lang-lowering/src/lower/mod.rs line 1390 at r1 (raw file):

Previously, orizi wrote…

how do we know this unwrap won't cause a panic?
same below.

because it worked before this change

[orizi]

Reviewed 2 of 5 files at r1.
Reviewable status: 4 of 5 files reviewed, 3 unresolved discussions (waiting on @ilyalesokhin-starkware)

---

crates/cairo-lang-lowering/src/lower/mod.rs line 1390 at r1 (raw file):

Previously, ilyalesokhin-starkware wrote…

because it worked before this change

so why does the query return Maybe?