[Copilot]

Diagnostics referencing an operation's parameter printed the anonymous model expression, e.g. TestService.{ param: TestService.Foo }.param, which is neither stable nor traceable back to the operation. getTypeName had no way to resolve the "parent" of a parameters model expression, so it fell back to the generic anonymous-model rendering.

Changes

• getModelName (packages/compiler/src/core/helpers/type-name-utils.ts): for an anonymous model, first attempt to resolve it as an operation's parameters.
• New getOperationParametersName: walks the syntax tree (ModelExpression → OperationSignatureDeclaration.parameters → OperationStatement) to render Namespace.op::parameters, including the interface prefix when the operation is on an interface, and op::parameters under nameOnly.
• Updated expectations in packages/versioning/test/incompatible-versioning.test.ts and the @overload case in packages/compiler/test/decorators/decorators.test.ts; added coverage in type-name-utils.test.ts.

Example

namespace TestService;

@added(Versions.v2)
model Foo {}

op test(param: Foo): void;

Before:

'TestService.{ param: TestService.Foo }.param' is referencing versioned type 'TestService.Foo' but is not versioned itself.

After:

'TestService.test::parameters.param' is referencing versioned type 'TestService.Foo' but is not versioned itself.

This also improves unrelated messages built on the same helper, e.g. @overload mismatches now read Property 'param' is missing on type 'someUnrelatedThing::parameters' but required in 'someThing::parameters'.

• Fixes [diagnostics]: inaccurate warning messages regarding incompatible verions #5863

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commit: bbca6c7

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All changed packages have been documented.

• ✅ @typespec/compiler

Show changes

@typespec/compiler - fix ✏️

Improve the name reported for an operation's parameters model expression. Diagnostics now refer to MyService.test::parameters.param instead of MyService.{ param: MyService.Foo }.param.

[Copilot]

Pull request overview

This PR improves diagnostic stability/readability by recognizing anonymous models that represent an operation’s parameters and naming them as Namespace.(Interface.)op::parameters (instead of rendering the anonymous model expression).

Changes:

• Updated getModelName to detect operation-parameter model expressions and format them as op::parameters (including interface prefix when applicable).
• Added getOperationParametersName to walk the syntax tree from ModelExpression → OperationSignatureDeclaration.parameters → OperationStatement.
• Updated/added test expectations and introduced focused unit tests for the new naming behavior; added a Chronus entry for the compiler fix.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/versioning/test/incompatible-versioning.test.ts	Updates expected diagnostics to use op::parameters-based naming.
packages/compiler/test/helpers/type-name-utils.test.ts	Adds unit coverage for operation-parameter naming (including interface + nameOnly).
packages/compiler/test/decorators/decorators.test.ts	Updates @overload error expectation to reflect new parameter-model naming.
packages/compiler/src/core/helpers/type-name-utils.ts	Implements detection/rendering of operation-parameter anonymous models as op::parameters.
.chronus/changes/improve-operation-parameters-type-name-2026-7-5.md	Adds changelog entry documenting the compiler diagnostic improvement.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Suppressed comments (2)

packages/compiler/test/helpers/type-name-utils.test.ts:67

• Avoid casting the resolved operation to any here; it bypasses type-checking and can hide errors if resolveTypeReference returns a non-operation type. You can keep this type-safe by asserting the resolved value is an Operation and using non-null assertions for the looked-up parameter.

    const [op] = program.resolveTypeReference("Foo.Bar.test");
    const param = (op as any).parameters.properties.get("param");

packages/compiler/test/helpers/type-name-utils.test.ts:77

• Avoid casting the resolved operation to any here; it bypasses type-checking and can hide errors if resolveTypeReference returns a non-operation type. You can keep this type-safe by asserting the resolved value is an Operation and using non-null assertions for the looked-up parameter.

    const [op] = program.resolveTypeReference("Foo.test");
    const param = (op as any).parameters.properties.get("param");