- Typecheck in all cases where a type may have changed
- Do not perform literal conversions if the type is already correct
- Perform literal conversions before checking to see if a call to
`__convert` is required. This catches cases such as string literals
passed where ints are required. Without this change, that form in
particular generates a bare number literal rather than a number
literal wrapped in a `__convert`.
Add a rewriter that reifies implicit conversions into a call to the
`__convert` intrinsic. Code generators can recognize this intrinsic and
use it to generate appropriate conversion code.
Part of this work involves redesigning the type annotations system.
Annotations are now only applicable to opaque and object types. Instead
of inspecting annotations directly, code generators should use
`hcl2.GetSchemaForType` to extract the `schema.Type` for a `model.Type`.
