Add spector test for alternate-type with emitter fixes for external types

[Copilot]

Adds spector test for azure/client-generator-core/alternate-type demonstrating external type replacement with geojson::Feature.

Changes

• Emitter: Handle non-discriminated unions in external types

  • Skip non-discriminated unions in adaptTypes() instead of failing
  • Return placeholder type in getType() when encountering unsupported unions
  • Prevents failures when external types contain complex property types that won't be emitted

• Emitter: Add numeric type support

  • Map TypeSpec numeric base type to f64

• Test infrastructure

  • Local client.tsp with Rust alternateType decorator mapping Feature → geojson::Feature
  • Tests validate external type usage in operations and model properties
  • Workspace integration with geojson dependency

Example

Generated code uses external type from geojson crate:

use geojson::Feature;

pub async fn get_model(&self) -> Result<Response<Feature>> { ... }

#[derive(Clone, Deserialize, Serialize)]
pub struct ModelWithFeatureProperty {
    pub feature: Option<Feature>,
    pub additional_property: Option<String>,
}

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add spector test for azure-http-specs\azure\client-generator-core\alternate-type</issue_title>
<issue_description>Do not modify the generated rust source code (in src/generated), only modify the emitter code (in /packages/typespec-rust/src/) if necessary.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add spector test for azure-http-specs\azure\client-generator-core\alternate-type\ #860

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[Copilot]

Pull request overview

This PR adds spector test coverage for the azure/client-generator-core/alternate-type spec, demonstrating external type replacement using the geojson::Feature crate. To support this, the emitter was enhanced to gracefully handle non-discriminated unions that appear in external types (which will be replaced and thus won't be emitted) and to support the TypeSpec numeric base type by mapping it to Rust's f64.

Changes:

• Enhanced emitter to skip non-discriminated unions in adaptTypes() instead of failing, since external types containing these unions will be replaced
• Added support for TypeSpec's numeric type by mapping it to f64 in Rust code generation
• Added comprehensive spector test suite for alternate-type feature with TypeSpec definitions, Cargo workspace integration, generated code, and integration tests

Reviewed changes

Copilot reviewed 8 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/typespec-rust/src/tcgcadapter/adapter.ts	Emitter enhancements: skip non-discriminated unions in adaptTypes() and getType(); map numeric type to f64
packages/typespec-rust/test/spector/azure/client-generator-core/alternate-type/main.tsp	TypeSpec definitions for Feature, Geometry, and test operations demonstrating external type usage
packages/typespec-rust/test/spector/azure/client-generator-core/alternate-type/client.tsp	Rust-specific alternateType decorator mapping Feature to geojson::Feature
packages/typespec-rust/test/spector/azure/client-generator-core/alternate-type/Cargo.toml	Package configuration with geojson dependency
packages/typespec-rust/test/Cargo.toml	Workspace member addition and geojson dependency declaration
packages/typespec-rust/test/Cargo.lock	Dependency lock file updates for geojson and transitive dependencies
packages/typespec-rust/test/spector/azure/client-generator-core/alternate-type/src/lib.rs	Library entry point
packages/typespec-rust/test/spector/azure/client-generator-core/alternate-type/src/generated/*	Generated client and model code using external geojson::Feature type
packages/typespec-rust/test/spector/azure/client-generator-core/alternate-type/tests/external_type_client.rs	Integration tests validating external type usage in operations and model properties
packages/typespec-rust/.scripts/tspcompile.js	Build script integration for the new test suite