Write a Rust type's constant fields as associated constants

[matt-edmondson]

Fixes #81

What changed

Inside a type, the Rust generator wrote every FieldDeclaration as a struct member and ignored IsStatic, IsConstant and InitialValue. So static constexpr int Limit = 8 came out as pub Limit: i32,: every constructor had to supply it, and the 8 was silently dropped.

• Static and constant fields no longer appear in the struct body. The new IsAssociatedField check treats a constant as static, as FieldDeclaration documents.
• A constant with a value is written into the type's inherent impl block as an associated const, for example pub const Limit: i32 = 8;. Callers name it through the type, as Cfg::Limit. The impl block now opens when the type has associated constants, even if it has no methods.
• A mutable static has no associated form in Rust. Neither does a constant with no value. For both, the generator writes a note through WriteInexpressible instead of dropping the field, which is what CLAUDE.md asks of the generators.

The insideType > 0 branch of GenerateFieldDeclaration is unchanged, because the struct loop never routes a field through it.

Tests

• RustGeneratorTests.ConstantField_IsAnAssociatedConstant: the struct holds only width, and impl Cfg holds const Limit: i32 = 8;.
• RustGeneratorTests.MutableStaticField_IsNotedRatherThanAStructField: no struct field is written, and a note is.
• RustGeneratedSourceCompilesTests: Boxed<T> now has a CAPACITY constant, and a method returns Self::CAPACITY, so rustc checks that the constant really is an associated item.

With the fix reverted, all three fail. rustc gives error[E0599]: no associated item named 'CAPACITY' found for struct 'Boxed<T>'. With the fix, the full suite passes: 915/915.

🤖 Generated with Claude Code

https://claude.ai/code/session_01NtawxkUssqE3PHcqRCW1Ag

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
85.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud