message: chore(cli) Remove the `--backend` deprecated option.
diff: //! commands.
  use crate::common::WasmFeatures;
  -use anyhow::{Error, Result};
  +use anyhow::Result;
  use clap::Clap;
  use std::path::PathBuf;
  -use std::str::FromStr;
  use std::string::ToString;
  #[allow(unused_imports)]
  use std::sync::Arc;
  @@ -36,15 +35,15 @@ pub struct StoreOptions {
  /// The compiler options
  pub struct CompilerOptions {
  /// Use Singlepass compiler.
  - #[clap(long, conflicts_with_all = &["cranelift", "llvm", "backend"])]
  + #[clap(long, conflicts_with_all = &["cranelift", "llvm"])]
  singlepass: bool,
  /// Use Cranelift compiler.
  - #[clap(long, conflicts_with_all = &["singlepass", "llvm", "backend"])]
  + #[clap(long, conflicts_with_all = &["singlepass", "llvm"])]
  cranelift: bool,
  /// Use LLVM compiler.
  - #[clap(long, conflicts_with_all = &["singlepass", "cranelift", "backend"])]
  + #[clap(long, conflicts_with_all = &["singlepass", "cranelift"])]
  llvm: bool,
  /// Enable compiler internal verification.
  @@ -55,10 +54,6 @@ pub struct CompilerOptions {
  #[clap(long, parse(from_os_str))]
  llvm_debug_dir: Option<PathBuf>,
  - /// The deprecated backend flag - Please do not use
  - #[clap(long = "backend", hidden = true, conflicts_with_all = &["singlepass", "cranelift", "llvm"])]
  - backend: Option<String>,
  -
  #[clap(flatten)]
  features: WasmFeatures,
  }
  @@ -72,12 +67,6 @@ impl CompilerOptions {
  Ok(CompilerType::LLVM)
  } else if self.singlepass {
  Ok(CompilerType::Singlepass)
  - } else if let Some(backend) = self.backend.clone() {
  - warning!(
  - "the `--backend={0}` flag is deprecated, please use `--{0}` instead",
  - backend
  - );
  - CompilerType::from_str(&backend)
  } else {
  // Auto mode, we choose the best compiler for that platform
  cfg_if::cfg_if! {
  @@ -344,19 +333,6 @@ impl ToString for CompilerType {
  }
  }
  -impl FromStr for CompilerType {
  - type Err = Error;
  - fn from_str(s: &str) -> Result<Self> {
  - match s {
  - "singlepass" => Ok(Self::Singlepass),
  - "cranelift" => Ok(Self::Cranelift),
  - "llvm" => Ok(Self::LLVM),
  - "headless" => Ok(Self::Headless),
  - backend => bail!("The `{}` compiler does not exist.", backend),
  - }
  - }
  -}
  -
  /// The engine used for the store
  #[derive(Debug, PartialEq, Eq, Clone, Copy)]
  pub enum EngineType {
  