[anneal][v2] Add exocrate toolchain setup and Toolchain resolver

TAG=agy

gherrit-pr-id: Gbbpbt76nsgp2ohpclea46vot5joxx7b5

Author: mdittmer

anneal/v2/src/setup.rs

@@ -0,0 +1,114 @@
+// Copyright 2026 The Fuchsia Authors
+//
+// Licensed under the 2-Clause BSD License <LICENSE-BSD or
+// https://opensource.org/license/bsd-2-clause>, Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// This file may not be copied, modified, or distributed except according to
+// those terms.
+
+use anyhow::Context as _;
+
+pub struct SetupArgs {
+    pub local_archive: Option<std::path::PathBuf>,
+}
+
+exocrate::config! {
+    pub const CONFIG: Config = Config {
+        rel_dir_path: [".anneal", "toolchain"],
+        versioned_files: &["../Cargo.toml", "../Cargo.lock"],
+    };
+}
+
+exocrate::parse_remote_archive! {
+    pub const REMOTE: RemoteArchive = "Cargo.toml" [
+        (linux, x86_64),
+        (macos, x86_64),
+        (linux, aarch64),
+        (macos, aarch64),
+    ];
+}
+
+pub enum Tool {
+    Charon,
+}
+
+impl Tool {
+    pub fn name(&self) -> &'static str {
+        match self {
+            Self::Charon => "charon",
+        }
+    }
+
+    pub fn path(&self, toolchain: &Toolchain) -> std::path::PathBuf {
+        match self {
+            Self::Charon => toolchain.aeneas_bin_dir().join(self.name()),
+        }
+    }
+}
+
+const AENEAS_DIR: &str = "aeneas";
+const RUST_SYSROOT: &str = "rust";
+const AENEAS_BIN_DIR: &str = "bin";
+const RUST_BIN_DIR: &str = "bin";
+const RUST_LIB_DIR: &str = "lib";
+
+pub struct Toolchain {
+    root: std::path::PathBuf,
+}
+
+impl Toolchain {
+    pub fn resolve() -> anyhow::Result<Self> {
+        let location = if std::env::var("__ANNEAL_LOCAL_DEV").is_ok() {
+            exocrate::Location::LocalDev
+        } else {
+            exocrate::Location::UserGlobal
+        };
+        let root = CONFIG
+            .resolve_installation_dir(location)
+            .context("Toolchain not installed. Please run 'cargo anneal setup' first.")?;
+        Ok(Self { root })
+    }
+
+    pub fn root(&self) -> &std::path::Path {
+        &self.root
+    }
+
+    pub fn aeneas_bin_dir(&self) -> std::path::PathBuf {
+        self.root.join(AENEAS_DIR).join(AENEAS_BIN_DIR)
+    }
+
+    pub fn rust_sysroot(&self) -> std::path::PathBuf {
+        self.root.join(RUST_SYSROOT)
+    }
+
+    pub fn rust_bin(&self) -> std::path::PathBuf {
+        self.rust_sysroot().join(RUST_BIN_DIR)
+    }
+
+    pub fn rust_lib(&self) -> std::path::PathBuf {
+        self.rust_sysroot().join(RUST_LIB_DIR)
+    }
+
+    pub fn command(&self, tool: Tool) -> std::process::Command {
+        std::process::Command::new(tool.path(self))
+    }
+}
+
+pub fn run_setup(args: SetupArgs) -> anyhow::Result<()> {
+    let location = if std::env::var("__ANNEAL_LOCAL_DEV").is_ok() {
+        exocrate::Location::LocalDev
+    } else {
+        exocrate::Location::UserGlobal
+    };
+    let source = match args.local_archive {
+        Some(local_archive) => exocrate::Source::Local(local_archive),
+        None => exocrate::Source::Remote(REMOTE),
+    };
+
+    let installation_dir = CONFIG
+        .resolve_installation_dir_or_install(location, source)
+        .context("failed to resolve-or-install dependencies")?;
+    log::info!("anneal toolchain is installed at {:?}", installation_dir);
+    Ok(())
+}