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Spec: Rewrite the type system fundamentals. #17447

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Merged
merged 7 commits into from
Jun 7, 2023
Merged

Spec: Rewrite the type system fundamentals. #17447

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8e65a2c
Spec: Rewrite the type system fundamentals.
sjrd May 9, 2023
978d4e4
Spec tweak: redefine designator types in terms of `memberType`.
sjrd May 10, 2023
6f21d93
Spec: Specify the desugaring of concrete refined types.
sjrd May 11, 2023
8657620
Move the concrete syntax of types to the beginning.
sjrd May 30, 2023
6021b7b
Make it clear that variance in concrete type lambdas are inferred.
sjrd May 30, 2023
a99f0b6
Spec: Address review comments except volatility.
sjrd Jun 6, 2023
254f23e
Spec: Replace volatility of types by the realizability concept.
sjrd Jun 7, 2023
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5 changes: 2 additions & 3 deletions docs/_docs/internals/syntax.md
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Expand Up @@ -201,7 +201,6 @@ SimpleType1 ::= id
Singleton ::= SimpleRef
| SimpleLiteral
| Singleton ‘.’ id
Singletons ::= Singleton { ‘,’ Singleton }
FunArgType ::= [`erased`] Type
| [`erased`] ‘=>’ Type PrefixOp(=>, t)
FunArgTypes ::= FunArgType { ‘,’ FunArgType }
Expand Down Expand Up @@ -357,8 +356,8 @@ ClsParam ::= {Annotation}
[{Modifier} (‘val’ | ‘var’) | ‘inline’] Param
DefParamClauses ::= DefParamClause { DefParamClause } -- and two DefTypeParamClause cannot be adjacent
DefParamClause ::= DefTypeParamClause
| DefTermParamClause
DefParamClause ::= DefTypeParamClause
| DefTermParamClause
| UsingParamClause
TypelessClauses ::= TypelessClause {TypelessClause}
TypelessClause ::= DefTermParamClause
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3 changes: 1 addition & 2 deletions docs/_docs/reference/new-types/intersection-types-spec.md
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Expand Up @@ -46,11 +46,10 @@ A & B <: B A & B <: A
In another word, `A & B` is the same type as `B & A`, in the sense that the two types
have the same values and are subtypes of each other.

If `C` is a type constructor, then `C[A] & C[B]` can be simplified using the following three rules:
If `C` is a co- or contravariant type constructor, then `C[A] & C[B]` can be simplified using the following rules:

- If `C` is covariant, `C[A] & C[B] ~> C[A & B]`
- If `C` is contravariant, `C[A] & C[B] ~> C[A | B]`
- If `C` is non-variant, emit a compile error

When `C` is covariant, `C[A & B] <: C[A] & C[B]` can be derived:

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2 changes: 1 addition & 1 deletion docs/_spec/02-identifiers-names-and-scopes.md
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Expand Up @@ -53,7 +53,7 @@ In that case, the type of ´x´ is the type of the referenced entity.

A reference to a qualified (type- or term-) identifier ´e.x´ refers to the member of the type ´T´ of ´e´ which has the name ´x´ in the same namespace as the identifier.
It is an error if ´T´ is not a [value type](03-types.html#value-types).
The type of ´e.x´ is the member type of the referenced entity in ´T´.
The type of ´e.x´ is specified as a [type designator](03-types.html#type-designators).

Binding precedence implies that the way source is bundled in files affects name resolution.
In particular, imported names have higher precedence than names, defined in other files, that might otherwise be visible because they are defined in either the current package or an enclosing package.
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