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Update the introduction of open and closed types. #1447

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Update the introduction of open and closed types. #1447

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2 changes: 1 addition & 1 deletion standard/types.md
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### 8.4.3 Open and closed types

Any type can be classified as either an ***open type*** or a ***closed type***. An open type is a type that involves type parameters. More specifically:
All types can be classified as either ***open types*** or ***closed types***. An open type is a type that involves type parameters. More specifically:
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@Nigel-Ecma Nigel-Ecma Oct 31, 2025

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The “can be” here should be something like “are” – we are defining things here. #1441 changes this line to:

Suggested change
All types can be classified as either ***open types*** or ***closed types***. An open type is a type that involves type parameters. More specifically:
Any type can be classified as either an ***open type*** or a ***closed type***. An open type is a type that involves type parameters. More specifically:

This still says “can be” so I think it is wrong. It also reads wrong to me, but that is subjective. I’m going to make some alternative suggestions, each in a seperate comment. Please 👍/👎🏻 as you see fit, including this one, and whomever merges can OK the preferred choice, or we don't merge and the #1441 version and “can be” stays.

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@Nigel-Ecma Nigel-Ecma Oct 31, 2025

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Suggested change
All types can be classified as either ***open types*** or ***closed types***. An open type is a type that involves type parameters. More specifically:
A type is classified as an ***open type*** or a ***closed type***. An open type is a type that involves type parameters. More specifically:

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@Nigel-Ecma Nigel-Ecma Oct 31, 2025

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Is “Every” better than “A”?

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All types can be classified as either ***open types*** or ***closed types***. An open type is a type that involves type parameters. More specifically:
Every type is classified as an ***open type*** or a ***closed type***. An open type is a type that involves type parameters. More specifically:

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@Nigel-Ecma Nigel-Ecma Oct 31, 2025

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Is “classified” really required?

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All types can be classified as either ***open types*** or ***closed types***. An open type is a type that involves type parameters. More specifically:
A type is either an ***open type*** or a ***closed type***. An open type is a type that involves type parameters. More specifically:

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@Nigel-Ecma Nigel-Ecma Oct 31, 2025

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The last one feels awkward, this seems better but loses defined terms, @RexJaeschke feel free to correct my use of italics in lieu!

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All types can be classified as either ***open types*** or ***closed types***. An open type is a type that involves type parameters. More specifically:
Every type is either **open** or **closed**. An open type is a type that involves type parameters. More specifically:

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@Nigel-Ecma Nigel-Ecma Oct 31, 2025

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Well those are my suggestions, all to remove “can be” – types are open/closed. Feel free to add your own of course :-)

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@BillWagner BillWagner Nov 3, 2025

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I'm OK with most of the alternatives.

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@RexJaeschke RexJaeschke Nov 7, 2025

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I prefer "A type is either an open type or a closed type. " for 2 reasons:

  1. When defining a term it's best to use the singular.
  2. I prefer "type" as part of the term being defined, as without it the terms open and closed are just adjectives with no context.

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@Nigel-Ecma Nigel-Ecma Nov 7, 2025

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With @RexJaeschke’s 👍 I think we have a winner (3 votes counting Rex), unless there are some late votes…


- A type parameter defines an open type.
- An array type is an open type if and only if its element type is an open type.
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> {
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