declarations file of extended class type is needlessly verbose (excessively deep) #54533
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Bug Report
When returning an extended class type from a function, the resulting
.d.ts
file is needlessly verbose resulting in very, very long.d.ts
for chained extensions. (See playground for details).🔎 Search Terms
emitDeclarations
polymorphic this
mixins
Base constructor must have same return type
Type instantiation is excessively deep and possibly infinite
🕗 Version & Regression Information
⏯ Playground Link
https://www.typescriptlang.org/play?target=7&ts=5.2.0-dev.20230605#code/MYGwhgzhAEDCCuEAuB7AtgURAUzdgdktNgB5IEAmMAEgCoCyAMlrgUQN4CwAUNNAPQAqQdB59oIgKoRsOKNGAp8yAE7xgqFdHzZsFPdFTQA7ihUBrMCpTx8FaLQDKYviIAGAIUjYFS1es0YNEQiMBAQaAALMAA3HyRInwgwPGgVbCR4FXxDAE8AB2wAOjcXCX4XRWUkNQ0zAAoipqsAcwgALmgwfFyASmguXnEIeEKVet6AbhcAXx4XIWgMMkoYWHAoIvzrVCQCn277dMzsmB1jOA2YQQqh5DAkAEtgaH0AM0edAB4yuEYAQUcjmIKzsMD2hRQbzgIXQLDwhAANL9-gAlADiwNI5DBcD8NQCZgAClYUhlsCoIF9YACgQA+ZFDPgASQAco5aP9WbAMCCcVRoMzqt1gNhaPtqbTHAzfkTUQB5IlY0EClAAIwAVtgNHTfvUEo8On9AY5EdAIDYVKLOnLFcCAGQOSKG8WFL62pXQR1sjlcnl03q-To0k1e6D1c7hppFVpGtGY-oAXjpgvZnO5vMdHsc-UG4jSGSyOXlmu1SCK70+2CJ1jGT2wEHqvz4BogWx2KAh2EZ+b4Fqyoq6MG6uR74n6kC6PWmQzm3DnPCEIgAYigUPC2EUNddbjxQJAYKv1zgEURsasYcg4Se2C4K9gPjp6nnxEu8WhT1EUHEtORkOVfkrHQKCFI8AEZOgJbtZkDIZ70fbBn0Ah8qxA-AjwAJk6AByNUrGwscZlgvh4KrJCmVeFDgNAtcAGZOlowjiOgUinxfPg30cDIYAwwwUGgbC3jXbCAIooSUHoDJIhQCgJgGZtDGdNsgL0GiUF4xMBPE7CZ3zOc+CIgZoAXbggA
💻 Code
🙁 Actual behavior
Here's the outputed d.ts:
🙂 Expected behavior
I expected
FooElement_base
to be shorter, smallerd.ts
like this:It seems repeated structures aren't analyzed and flattened. I also don't see a way to flatten them myself. Changing
CLASS
to{[P in keyof CLASS]: CLASS[P]}
will make each item reiterate every single property inHTMLElement
in the d.ts.This is a short reproducible, but actual code can get really heavy especially with mixins. I believe (but can't confirm), it causes the "Type instantiation is excessively deep and possibly infinite" error as well. There's probably a performance gain somewhere here as well. I know
TS
will flatten types, but not constructor return arguments. Maybe, simplified that's the core issue.I have a second playground link that has a more verbose example including mixin patterns and extending classes extending classes:
https://www.typescriptlang.org/play?target=7&ts=5.2.0-dev.20230605#code/C4TwDgpgBAwgNgQwM5IPIDMA8AVKEAewEAdgCZJQDeUYATgPbCPgQBcUArsQNbH0DuxANxQAvgD4oAXijYhAWABQSgMaIUsDkiYBbAKJwIOksDyES5KAAlsAWQAyBoyapKoUAPQAqL1DfvfAFUkCEMNFXpibVoOFSZaKGIICFIUqCYofnpabgQGLlJZAGV-KF8AAwAhZGgIqOAYuOyKHS1TBDg4KAALBAA3aGBu6CQEYyhaCGAOWmJ0lgA6ctKvD3866Nj4gAoFvbyAcyR2BGIQAEpXRXd3JA5IWm3zhWuxJX9tBGAASxUzIjIOH+FgooEg9HQmm09H0hmMxGA4m2Q2+x1k51YuEopQmUxmczUyAoBABlhRFEoohe7lE71enx+fx033w32ImBxlQAgkU9MCyKCWBCobonPDgAAaHEAMQAcvzLLt9rQjiczgBtAC6lykklOIClr3cACU9NhAsb5SSQVBjXjZtgWJg5eJDTcoEVApUYPYeUUFRR4ESMJhTebLa6cVzjQBxf3WgWwSKbJq0AAKeTGUwgtCQmE93t9RSKkaNUG5vIA+gBJWVFbBc2UwPkJyzV+qnFQQR2QTAVvSl90Fn1+mt1htNlvmRPtz7ELs9iD5r0j4vicQ45HdVHsfsSqDM1nEdhyjEeldF-0AMnLPL0OJv2yS-CgSoWhzR0bjOskw8vY-rRtmygG9+wAidm0ubEy0maZZgPFk2S3VFnn8WllFebwoD0adLCDFAFjoRhmEgKBTkKWD8QoZ9YHUChVg+YAvl+KBUnQNklxxVd41wwVwUhGA2hhMUTDdG4vx40lA2TBotmyDNaCzIhc0wbjBxuWtAMnAMoFnJj527J01LE9w02NVA00km16AAIwAKwgOINzLZC0W4-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-ccuOPTssfaKKYKBz9J6CgbH0H17Gw5xEf6FsKZunoUgniub6pszmP9f7nHJ+xyWaRLqg3gwn3qloQ2+pN8fzbo8s8hPnSrZP9uPfBlfiCP+PEg4TpDWlxeibooa4pGiAdsR8XjrBko0HYfNnxchVGiaIbIDhak6mWO4Dwnjb3SEFBYFskD-yykAl+eRpCJBqjAo4GslBa0UD7K2thELEGNqbJQ6AuBxG+JEKAtD6HbBUA7E+HMhQCT4TbBEyD3CUXgrw6EjtxQP0rhnGuUdV5T3oW-Gi2UvhpzlmWZ+XCjx5ygOgDoIQFq6P1nQo8jch7wOIAcYurxpYvCoYfBAAAve+Z8GIXyJFfdxIjTB2yvsffxF1uF6LZGIzwPg-BGiCCEMIFANiyVTCQlIaQMhZByHkLyZBigrCgFUGoRNwFyVzAeNoZFOg9H6IMYYUBRjjAkcrRYyxYnh2KfUCB2Q6qwNYPqJBP9bj3BzD0o4Csd7XGcdEo+Fi2SMPPiw+cgsgmzOIDw4RTtgACP4iKYS-jIlNKJhs2RqdO4R0USkYBeRVlv05qYi5WcZn0IMfXAArPciujzrn0KsdjGxdiW5OLpD7XKhJFI-AGB4ph1DonZXoHlYg2NTBJDSFoUIeVEklJSV41QMkoCgsQJMUgN8ZDVD8Zsl2rYngu0PEhJ5R5W681OVXZ+BK8gpBPm-AAHMjQFdIknVzBRy-xxD1GOUJcKzZ6ClCpCFcSkJZj6Cx2IZzF4sqJXys2XIuua9iEFyLi8DwHgoAAAFgBIAALQEEgHEK1tAGAJCQLPD+hQjHfDgDK8V7LNUnIeco+uxCjFwBCGqr1RL76T2nkMOe0rFDqu9ffZ+r9RUfzgKGuV98cF4MAVc2gCxDC2KGOmjVia-XZ3MaohYBwpgaKILG+N4aFVlvpWyHOCwmDShZCkbYOcFYNslb6z57Y2WNs2bHdt9BO34G7QrJQQA
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