Remove the CodeOracle (#1591)

* Remove the CodeOracle

This is now purely a local consideration for bindings, there's
no need for a shared trait. This removes a lot of unnecessary code.

* More kotlin improvements: enum/error variants now work as a CodeType.

uniffi_bindgen/src/backend/mod.rs

@@ -3,13 +3,8 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 mod config;
-mod declarations;
-mod oracle;
 mod types;
 
+pub use crate::interface::{Literal, Type};
 pub use config::TemplateExpression;
-pub use declarations::CodeDeclaration;
-pub use oracle::CodeOracle;
 pub use types::CodeType;
-
-pub use crate::interface::{Literal, Type};

uniffi_bindgen/src/backend/types.rs

@@ -4,27 +4,12 @@
 
 //! # Backend traits
 //!
-//! This module provides a number of traits useful for implementing a backend for Uniffi.
+//! A trait to help format items.
 //!
-//! A `CodeType` is needed for each type that will cross the FFI. It should provide helper machinery
-//! in the target language to lift from and lower into a value of that type into a primitive type
-//! (the FfiType), and foreign language expressions that call into the machinery. This helper code
-//! can be provided by a template file.
-//!
-//! The `CodeOracle` provides methods to map the `Type` values found in the `ComponentInterface` to the `CodeType`s specified
-//! by the backend. It also provides methods for transforming identifiers into the coding standard for the target language.
-//!
-//! There's also a CodeTypeDispatch trait, implemented for every type, which allows a CodeType to be created
-//! by the specified `CodeOracle`. This means backends are able to provide a custom CodeType for each type
-//! via that backend's CodeOracle.
-//!
-//! Each backend will have its own `filter` module, which is used by the askama templates used in all `CodeType`s and `CodeDeclaration`s.
-//! This filter provides methods to generate expressions and identifiers in the target language. These are all forwarded to the oracle.
-
+//! Each backend will have its own `filter` module, which is used by the askama templates.
+use super::Literal;
 use std::fmt::Debug;
 
-use crate::interface::*;
-
 /// A Trait to help render types in a language specific format.
 pub trait CodeType: Debug {
     /// The language specific label used to reference this type. This will be used in
@@ -40,8 +25,6 @@ pub trait CodeType: Debug {
         self.type_label()
     }
 
-    /// A representation of the given literal for this type.
-    /// N.B. `Literal` is aliased from `interface::Literal`, so may not be whole suited to this task.
     fn literal(&self, _literal: &Literal) -> String {
         unimplemented!("Unimplemented for {}", self.type_label())
     }

uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::backend::{CodeType, Literal};
 
 #[derive(Debug)]
 pub struct CallbackInterfaceCodeType {

uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use crate::backend::{CodeOracle, CodeType, Literal, Type};
+use crate::backend::{CodeType, Literal, Type};
 use paste::paste;
 
 fn render_literal(literal: &Literal, inner: &Type) -> String {

uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::backend::{CodeType, Literal};
 
 #[derive(Debug)]
 pub struct EnumCodeType {

uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::backend::{CodeType, Literal};
 
 #[derive(Debug)]
 pub struct ErrorCodeType {