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.
691b98b612