feat: inline named model expressions

[Copilot]

Adds support for defining named models inline in type expression positions:

model Parent {
  child: model Child {
    grandchild: model Grandchild {
      age: int32;
    };
  };
}

@@doc(Child, "The child model");
@@doc(Grandchild, "The grandchild model");

Inline named models are declared in the enclosing namespace/script scope, making them referenceable by augment decorators and subject to standard duplicate-name detection. Arbitrarily deep nesting is supported.

Compiler

• AST (types.ts): Optional id: IdentifierNode on ModelExpressionNode
• Parser (parser.ts): ModelKeyword case in parsePrimaryExpression dispatches to parseInlineNamedModelExpression(); visitChildren traverses optional id
• Binder (binder.ts): bindModelExpression uses getEnclosingDeclarationScope() to walk up to the nearest namespace/script scope for symbol declaration
• Checker (checker.ts): checkModelExpression uses explicit createType (matching checkModelStatement pattern), sets Model.name from node.id, processes augment decorators for named inline models
• Formatter (printer.ts): Emits model <Name> prefix for named model expressions

Grammar & Semantic Tokens

• inlineNamedModelExpression TextMate rule for model <Name> { ... } in expression position
• statementKeywordExceptModel / universalEndExceptModel prevent model from prematurely terminating type annotation and model property contexts
• classify.ts handles ModelExpression with id for semantic token highlighting

Tests

• Parser: deep nesting (2/3 levels), missing-name error
• Checker positive: augment decorators, nested models, deep nesting + augment decorators, spread properties
• Checker negative: duplicate sibling names, conflict with top-level model, nested name reuse
• Typekit: model.is(), model.getEffectiveModel(), type.getPlausibleName(), type.clone(), type.isAssignableTo(), type.resolve()
• Colorization: semantic + tmlanguage tokenization

Sample

Updated playground http.tsp with inline named models in a model property, operation response, and template parameter position.

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[johanste]

@copilot update the changelog

[Copilot]

@copilot update the changelog

Added the changelog entry in commit 6ac054e.

[johanste]

@copilot fix the failing checks

[Copilot]

@copilot fix the failing checks

Fixed in b0d2b6d:

• Removed unused program variable in test/typekit/model.test.ts (lint warning)
• Reformatted test/parser.test.ts (prettier formatting)

[github-actions]

All changed packages have been documented.

• ✅ @typespec/compiler

Show changes

@typespec/compiler - feature ✏️

Add support for inline named model expressions in property type positions