Introduce a ModuleResult alias for Result<T, ModuleError>.

This follows the pattern used by cretonne-codegen, cretonne-wasm, and
others.

lib/faerie/src/backend.rs

@@ -5,7 +5,7 @@ use cretonne_codegen::binemit::{Addend, CodeOffset, NullTrapSink, Reloc, RelocSi
 use cretonne_codegen::isa::TargetIsa;
 use cretonne_codegen::{self, binemit, ir};
 use cretonne_module::{Backend, DataContext, DataDescription, Init, Linkage, ModuleError,
-                      ModuleNamespace};
+                      ModuleNamespace, ModuleResult};
 use faerie;
 use failure::Error;
 use std::fs::File;
@@ -52,7 +52,7 @@ impl FaerieBuilder {
         format: BinaryFormat,
         collect_traps: FaerieTrapCollection,
         libcall_names: Box<Fn(ir::LibCall) -> String>,
-    ) -> Result<Self, ModuleError> {
+    ) -> ModuleResult<Self> {
         if !isa.flags().is_pic() {
             return Err(ModuleError::Backend(
                 "faerie requires TargetIsa be PIC".to_owned(),
@@ -149,7 +149,7 @@ impl Backend for FaerieBackend {
         ctx: &cretonne_codegen::Context,
         namespace: &ModuleNamespace<Self>,
         code_size: u32,
-    ) -> Result<FaerieCompiledFunction, ModuleError> {
+    ) -> ModuleResult<FaerieCompiledFunction> {
         let mut code: Vec<u8> = Vec::with_capacity(code_size as usize);
         code.resize(code_size as usize, 0);
 
@@ -198,7 +198,7 @@ impl Backend for FaerieBackend {
         name: &str,
         data_ctx: &DataContext,
         namespace: &ModuleNamespace<Self>,
-    ) -> Result<FaerieCompiledData, ModuleError> {
+    ) -> ModuleResult<FaerieCompiledData> {
         let &DataDescription {
             writable: _writable,
             ref init,

lib/module/src/backend.rs

@@ -8,6 +8,7 @@ use DataContext;
 use Linkage;
 use ModuleError;
 use ModuleNamespace;
+use ModuleResult;
 
 /// A `Backend` implements the functionality needed to support a `Module`.
 pub trait Backend
@@ -57,7 +58,7 @@ where
         ctx: &Context,
         namespace: &ModuleNamespace<Self>,
         code_size: u32,
-    ) -> Result<Self::CompiledFunction, ModuleError>;
+    ) -> ModuleResult<Self::CompiledFunction>;
 
     /// Define a zero-initialized data object of the given size.
     ///
@@ -67,7 +68,7 @@ where
         name: &str,
         data_ctx: &DataContext,
         namespace: &ModuleNamespace<Self>,
-    ) -> Result<Self::CompiledData, ModuleError>;
+    ) -> ModuleResult<Self::CompiledData>;
 
     /// Write the address of `what` into the data for `data` at `offset`. `data` must refer to a
     /// defined data object.

lib/module/src/lib.rs

@@ -33,7 +33,8 @@ mod module;
 
 pub use backend::Backend;
 pub use data_context::{DataContext, DataDescription, Init, Writability};
-pub use module::{DataId, FuncId, FuncOrDataId, Linkage, Module, ModuleError, ModuleNamespace};
+pub use module::{DataId, FuncId, FuncOrDataId, Linkage, Module, ModuleError, ModuleNamespace,
+                 ModuleResult};
 
 /// This replaces `std` in builds with `core`.
 #[cfg(not(feature = "std"))]

lib/module/src/module.rs

@@ -139,6 +139,9 @@ pub enum ModuleError {
     Backend(String),
 }
 
+/// A convenient alias for a `Result` that uses `ModuleError` as the error type.
+pub type ModuleResult<T> = Result<T, ModuleError>;
+
 /// A function belonging to a `Module`.
 struct ModuleFunction<B>
 where
@@ -347,7 +350,7 @@ where
         name: &str,
         linkage: Linkage,
         signature: &ir::Signature,
-    ) -> Result<FuncId, ModuleError> {
+    ) -> ModuleResult<FuncId> {
         // TODO: Can we avoid allocating names so often?
         use std::collections::hash_map::Entry::*;
         match self.names.entry(name.to_owned()) {
@@ -385,7 +388,7 @@ where
         name: &str,
         linkage: Linkage,
         writable: bool,
-    ) -> Result<DataId, ModuleError> {
+    ) -> ModuleResult<DataId> {
         // TODO: Can we avoid allocating names so often?
         use std::collections::hash_map::Entry::*;
         match self.names.entry(name.to_owned()) {
@@ -457,7 +460,7 @@ where
     }
 
     /// Define a function, producing the function body from the given `Context`.
-    pub fn define_function(&mut self, func: FuncId, ctx: &mut Context) -> Result<(), ModuleError> {
+    pub fn define_function(&mut self, func: FuncId, ctx: &mut Context) -> ModuleResult<()> {
         let compiled = {
             let code_size = ctx.compile(self.backend.isa()).map_err(|e| {
                 dbg!(
@@ -489,7 +492,7 @@ where
     }
 
     /// Define a function, producing the data contents from the given `DataContext`.
-    pub fn define_data(&mut self, data: DataId, data_ctx: &DataContext) -> Result<(), ModuleError> {
+    pub fn define_data(&mut self, data: DataId, data_ctx: &DataContext) -> ModuleResult<()> {
         let compiled = {
             let info = &self.contents.data_objects[data];
             if !info.compiled.is_none() {

lib/simplejit/src/backend.rs

@@ -3,8 +3,8 @@
 use cretonne_codegen::binemit::{Addend, CodeOffset, NullTrapSink, Reloc, RelocSink};
 use cretonne_codegen::isa::TargetIsa;
 use cretonne_codegen::{self, ir, settings};
-use cretonne_module::{Backend, DataContext, DataDescription, Init, Linkage, ModuleError,
-                      ModuleNamespace, Writability};
+use cretonne_module::{Backend, DataContext, DataDescription, Init, Linkage, ModuleNamespace,
+                      ModuleResult, Writability};
 use cretonne_native;
 use libc;
 use memory::Memory;
@@ -118,7 +118,7 @@ impl<'simple_jit_backend> Backend for SimpleJITBackend {
         ctx: &cretonne_codegen::Context,
         _namespace: &ModuleNamespace<Self>,
         code_size: u32,
-    ) -> Result<Self::CompiledFunction, ModuleError> {
+    ) -> ModuleResult<Self::CompiledFunction> {
         let size = code_size as usize;
         let ptr = self.code_memory
             .allocate(size)
@@ -141,7 +141,7 @@ impl<'simple_jit_backend> Backend for SimpleJITBackend {
         _name: &str,
         data: &DataContext,
         _namespace: &ModuleNamespace<Self>,
-    ) -> Result<Self::CompiledData, ModuleError> {
+    ) -> ModuleResult<Self::CompiledData> {
         let &DataDescription {
             writable,
             ref init,