1 files changed, 110 insertions, 0 deletions
diff --git a/compiler/rustc_span/src/edition.rs b/compiler/rustc_span/src/edition.rs
new file mode 100644
index 000000000..065d3660e
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+++ b/compiler/rustc_span/src/edition.rs
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+use crate::symbol::{sym, Symbol};
+use std::fmt;
+use std::str::FromStr;
+
+use rustc_macros::HashStable_Generic;
+
+/// The edition of the compiler. (See [RFC 2052](https://github.com/rust-lang/rfcs/blob/master/text/2052-epochs.md).)
+#[derive(Clone, Copy, Hash, PartialEq, PartialOrd, Debug, Encodable, Decodable, Eq)]
+#[derive(HashStable_Generic)]
+pub enum Edition {
+    // When adding new editions, be sure to do the following:
+    //
+    // - update the `ALL_EDITIONS` const
+    // - update the `EDITION_NAME_LIST` const
+    // - add a `rust_####()` function to the session
+    // - update the enum in Cargo's sources as well
+    //
+    // Editions *must* be kept in order, oldest to newest.
+    /// The 2015 edition
+    Edition2015,
+    /// The 2018 edition
+    Edition2018,
+    /// The 2021 edition
+    Edition2021,
+    /// The 2024 edition
+    Edition2024,
+}
+
+// Must be in order from oldest to newest.
+pub const ALL_EDITIONS: &[Edition] =
+    &[Edition::Edition2015, Edition::Edition2018, Edition::Edition2021, Edition::Edition2024];
+
+pub const EDITION_NAME_LIST: &str = "2015|2018|2021|2024";
+
+pub const DEFAULT_EDITION: Edition = Edition::Edition2015;
+
+pub const LATEST_STABLE_EDITION: Edition = Edition::Edition2021;
+
+impl fmt::Display for Edition {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match *self {
+            Edition::Edition2015 => "2015",
+            Edition::Edition2018 => "2018",
+            Edition::Edition2021 => "2021",
+            Edition::Edition2024 => "2024",
+        };
+        write!(f, "{}", s)
+    }
+}
+
+impl Edition {
+    pub fn lint_name(&self) -> &'static str {
+        match *self {
+            Edition::Edition2015 => "rust_2015_compatibility",
+            Edition::Edition2018 => "rust_2018_compatibility",
+            Edition::Edition2021 => "rust_2021_compatibility",
+            Edition::Edition2024 => "rust_2024_compatibility",
+        }
+    }
+
+    pub fn feature_name(&self) -> Symbol {
+        match *self {
+            Edition::Edition2015 => sym::rust_2015_preview,
+            Edition::Edition2018 => sym::rust_2018_preview,
+            Edition::Edition2021 => sym::rust_2021_preview,
+            Edition::Edition2024 => sym::rust_2024_preview,
+        }
+    }
+
+    pub fn is_stable(&self) -> bool {
+        match *self {
+            Edition::Edition2015 => true,
+            Edition::Edition2018 => true,
+            Edition::Edition2021 => true,
+            Edition::Edition2024 => false,
+        }
+    }
+
+    pub fn rust_2015(&self) -> bool {
+        *self == Edition::Edition2015
+    }
+
+    /// Are we allowed to use features from the Rust 2018 edition?
+    pub fn rust_2018(&self) -> bool {
+        *self >= Edition::Edition2018
+    }
+
+    /// Are we allowed to use features from the Rust 2021 edition?
+    pub fn rust_2021(&self) -> bool {
+        *self >= Edition::Edition2021
+    }
+
+    /// Are we allowed to use features from the Rust 2024 edition?
+    pub fn rust_2024(&self) -> bool {
+        *self >= Edition::Edition2024
+    }
+}
+
+impl FromStr for Edition {
+    type Err = ();
+    fn from_str(s: &str) -> Result<Self, ()> {
+        match s {
+            "2015" => Ok(Edition::Edition2015),
+            "2018" => Ok(Edition::Edition2018),
+            "2021" => Ok(Edition::Edition2021),
+            "2024" => Ok(Edition::Edition2024),
+            _ => Err(()),
+        }
+    }
+}