The console-only `type` function allows interrogation of any value's
type. An implementation quirk is that we use a cty.Mark to allow the
console to display this type information without the usual HCL quoting.
For example:
> type("boop")
string
instead of:
> type("boop")
"string"
Because these marks can propagate when used in complex expressions,
using the type function as part of a complex expression could result in
this "print as raw" mark being attached to a collection. When this
happened, it would result in a crash when we tried to iterate over a
marked value.
The `type` function was never intended to be used in this way, which is
why its use is limited to the console command. Its purpose was as a
pseudo-builtin, used only at the top level to display the type of a
given value.
This commit goes some way to preventing the use of the `type` function
in complex expressions, by refusing to display any non-string value
which was marked by `type`, or contains a sub-value which was so marked.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.
Alisdair McDiarmid