Detect model spread cycles without over-reporting recursive model-expression aliases

[Copilot]

Model-to-model spread cycles were not being validated correctly (Foo spreads Bar, Bar spreads Foo), which led to unresolved checker state instead of a proper diagnostic. At the same time, alias recursion through model expressions was being flagged too aggressively.

• Spread cycle validation

  • Adds explicit cycle detection for model spread chains in the checker.
  • Mutual spreads now surface the intended spread-model self-spread diagnostic instead of ending in pending-resolution failure.

• Alias recursion behavior

  • Narrows circular-alias handling for aliases whose value is a model expression.
  • Allows recursive object-shape aliases (via model expressions) to resolve without emitting circular-alias-type.

• Targeted test coverage

  • Unskips and enforces the mutual spread regression case in spread.test.ts.
  • Adds a regression case in alias.test.ts for recursive aliases through model expressions.

model Foo { ...Bar }
model Bar { ...Foo } // now diagnosed as spread-model self-spread

alias A = { a: B };
alias B = { a: A }; // now allowed (no circular-alias-type)

Warning

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I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /opt/hostedtoolcache/node/22.22.2/x64/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/bin/astro.mjs build node s/.b�� run --local de_modules/pnpm/dist/node-gyp-bin/node import @typespecsh --production reams/reference node sion�� build.json dotnet k/typespec/typespec/node_modules/.bin/node --no-emit node rsioning/referendoc sh (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/compiler@10684

commit: 8312634

[timotheeguerin]

@copilot add changelog

[Copilot]

@copilot add changelog

Added in d5224a2: created a Chronus changelog entry for @typespec/compiler under .chronus/changes/copilot-fix-model-circular-references-2026-4-14-20-45-42.md.

[timotheeguerin]

@copilot pull in change from main and resolve conflicts

[Copilot]

@copilot pull in change from main and resolve conflicts

Done in 6430064 — pulled latest main, resolved the merge conflict in packages/compiler/src/core/checker.ts, and pushed the merge commit.

[github-actions]

All changed packages have been documented.

• ✅ @typespec/compiler

Show changes

@typespec/compiler - fix ✏️

Fixed the compiler to correctly detect circular model spread chains while preserving support for recursive model-expression aliases.

[azure-sdk-automation]

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