Update declaring constructors to allow the new constructor syntax #4543
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Testing the libraries in A couple of errors arise because the test specifically tests the treatment of built-in identifiers and reserved words, so that's to be expected. The remaining errors are all concerned with the use of We could try out the radical approach (making |
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| <classDeclaration> ::= // First alternative modified. | ||
| (<classModifiers> | <mixinClassModifiers>) | ||
| 'class' <classNamePart> <superclass>? <interfaces>? <classBody> | ||
| 'class' <classNameMaybePrimary> <superclass>? <interfaces>? <classBody> |
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Suggestion/nit: "maybe" implies "optional" to me but not a choice from two alternatives. Perhaps a better name is "classNameOrPrimary"?
| <typeIdentifier> <typeParameters>? | ||
| ('.' <identifierOrNew>)? <declaringParameterList> | ||
| <primaryConstructor> ::= // New rule. | ||
| 'const'? <typeWithParameters> ('.' <identifierOrNew>)? |
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For what it's worth, I never thought there was value in supporting Foo.new in constructor declarations, and we don't necessarily have to support it for primary constructors. We could just do ('.' <identifier>) here.
But if you think it's worth it for consistency, I could go either way. :)
| *This allows the new constructor declaration syntax such as `factory();` to | ||
| be unambiguous. It is also a breaking change because `factory` can no | ||
| longer be the name of a declaration. However, this occurs only infrequently | ||
| today.* |
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We should be explicit here that this is a language versioned change. We'd say that factory is a built-in identifier in pre-feature libraries and a reserved word in later versions.
| <constantConstructorSignature> ::= // Modified rule. | ||
| : 'const' <constructorName> <formalParameterList> // Old form. | ||
| | 'const' <constructorHead> <formalParameterList> // New form. |
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All the "old form" / "new form" comments are very helpful here.
See #4485 for background information.
This PR changes the feature specification of declaring constructors such that its grammar rules support the new style of constructor declarations (like
new();andconst factory name() = D;).It handles the ambiguity among
factory();being a method or a factory constructor declaration whose name is the name of the enclosing class/mixin-class/enum/extension-type declaration by makingfactorya reserved word.