feat(compiler): add @strictExtends to require union variants to nominally extend the base type - #11780

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JoshLove-msft wants to merge 11 commits into

microsoft:mainfrom

JoshLove-msft:josh/union-strict-extends

Commits on Aug 27, 2026

feat(compiler): add `extends` base type clause for unions

JoshLove-msft
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ff0bed2
feat(compiler): add `@strictExtends` to require union variants to extend the base type

JoshLove-msft
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cf859a2
fix(compiler): fix stack overflow when checking assignability of recursive types

JoshLove-msft
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358fc12
Merge branch 'josh/fix-relation-cycle' into josh/union-strict-extends
JoshLove-msft
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69ca929
feat(compiler): harden @strictExtends validation

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b955e41
Merge remote-tracking branch 'upstream/main' into josh/union-extends
JoshLove-msft
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c383951
Merge branch 'josh/union-extends' into josh/union-strict-extends
JoshLove-msft
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47177e7
fix(compiler): make @strictExtends validation order and mutation safe

JoshLove-msft
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d4d9d0f
fix(compiler): validate @strictExtends unions created after checking

JoshLove-msft
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2e87605
fix(compiler): run onGraphFinish validators for types created after checking

JoshLove-msft
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75a1042
docs(compiler): note the graph finish validator limitation for post-check types
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8e8cddf