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Start stubbing out more parts of Type::join(). #14698

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Merged
merged 1 commit into from
Mar 1, 2018
Merged

Start stubbing out more parts of Type::join(). #14698

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16 changes: 10 additions & 6 deletions include/swift/AST/Type.h
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Original file line number Diff line number Diff line change
Expand Up @@ -368,15 +368,19 @@ class Type {
/// class D { }
/// \endcode
///
/// The join of B and C is A, the join of A and B is A. However, there is no
/// join of D and A (or D and B, or D and C) because there is no common
/// superclass. One would have to jump to an existential (e.g., \c AnyObject)
/// to find a common type.
/// The join of B and C is A, the join of A and B is A.
///
/// The Any type is considered the common supertype by default when no
/// closer common supertype exists.
///
/// In unsupported cases where we cannot yet compute an accurate join,
/// we return None.
///
/// \returns the join of the two types, if there is a concrete type
/// that can express the join, or Any if the only join would be a
/// more-general existential type
static Type join(Type first, Type second);
/// more-general existential type, or None if we cannot yet compute a
/// correct join but one better than Any may exist.
static Optional<Type> join(Type first, Type second);

private:
// Direct comparison is disabled for types, because they may not be canonical.
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