[adamcavendish]

Summary

Follow up #156 with six tests covering shared Rust error generation through the public CodeGenerator::generate boundary.

• Pin exact error-enum output for arrays, nullable arrays, maps, primitive and model aliases, long map payloads, bodyless errors, and JSON/text/binary payloads across reqwest, ureq, and aioduct.
• Exercise nested nullable/alias combinations directly from IR and verify a real sigil-stitch failure returns GeneratorError::Emission with API and original source context instead of panicking.
• Compile the new fixture's generated clients for all three Rust backends.

Coverage

Paired cargo llvm-cov runs used the library tests and the three existing Rust golden suites; the second run additionally included rust_error_generation.

Shared emitter	Before	After
src/generators/rust/common/emit_api.rs line coverage	1043/1144	1061/1144
Percentage	91.17%	92.74%

These are scoped line-coverage measurements, not repository-wide or value-weighted coverage percentages.

Boundaries

• Tests and fixture only: no production behavior, dependencies, existing goldens, or release versions change.
• Failure propagation uses deliberately invalid lowered IR, not a test-only hook or a claim that valid OpenAPI input should be rejected.
• New generated-client checks prove compilation, not live HTTP decoding of every composite payload.
• An existing OAS 3.0 lowering issue drops nullable within map values. That cross-language issue remains outside this PR; the direct-IR cases independently protect nested-nullable generator behavior.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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