Rustfmt and update docs

cranelift/module/README.md

@@ -6,14 +6,13 @@ This crate is structured as an optional layer on top of cranelift-codegen.
 It provides additional functionality, such as linking, however users that
 require greater flexibility don't need to use it.
 
-A `Module` is a collection of functions and data objects that are linked
-together. `Backend` is a trait that defines an interface for backends
-that compile modules into various forms. Most users will use one of the
-following `Backend` implementations:
+A module is a collection of functions and data objects that are linked
+together. The `Module` trait that defines a common interface for various kinds
+of modules. Most users will use one of the following `Module` implementations:
 
- - `SimpleJITBackend`, provided by [cranelift-simplejit], which JITs
+ - `SimpleJITModule`, provided by [cranelift-simplejit], which JITs
    code to memory for direct execution.
- - `ObjectBackend`, provided by [cranelift-object], which emits native
+ - `ObjectModule`, provided by [cranelift-object], which emits native
    object files.
 
 [cranelift-simplejit]: https://crates.io/crates/cranelift-simplejit

cranelift/module/src/data_context.rs

@@ -50,7 +50,8 @@ pub struct DataDescription {
     pub data_relocs: Vec<(CodeOffset, ir::GlobalValue, Addend)>,
     /// Object file section
     pub custom_segment_section: Option<(String, String)>,
-    /// Alignment
+    /// Alignment in bytes. `None` means that the default alignment of the respective module should
+    /// be used.
     pub align: Option<u64>,
 }
 

cranelift/module/src/module.rs

@@ -142,7 +142,7 @@ impl FunctionDeclaration {
     }
 }
 
-/// Error messages for all `Module` and `Backend` methods
+/// Error messages for all `Module` methods
 #[derive(Error, Debug)]
 pub enum ModuleError {
     /// Indicates an identifier was used before it was declared