Maybe this will help: all record types already exist when the type checker
starts. Even though there are no terms of that type, you could write x = {
bar = "foo" } and that value will be assigned the type { bar : String },
notice the equals in the value and the colon in the type.
So, type aliasing a record is just like type aliasing an Int: It doesn't
increase the number of types available, it just adds a new name (alias) for
an existing type.
Meanwhile the type keyword, no alias, creates a union type, which you say
you understand. Point being that a union type is a new type, which could
not be written before it was defined. (Record constructors are useful
shorthand, but if hypothetically the language didn't provide them, there
wouldn't be any programs that would become unwritable because of that
change.
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