go/types: add Basic.Obj

[adonovan]

A types.Basic has a name (TypeName). For consistency, it should have an Obj() method, like Alias, Named, and TypeParam.

 package types

+ // Obj returns the type name for the built-in declaration defining the basic type b.
+ func (b *Basic) Obj() *TypeName { return Universe.Lookup(b.name).(*TypeName) }

Context: https://go.dev/cl/650755

Perhaps we should also add this interface:

// A TypeWithName is a [Type] with a name ([TypeName]).
// It is implemented by [*Alias], [*Basic], [*Named], and [*TypeParam].
type TypeWithName interface {
       Type
       Obj() *TypeName
}

@griesemer @jba @findleyr

[gabyhelp]

Related Issues

• proposal: go/types: add HasTypeName interface #66890

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