Add edition default support

Author: nyurik

bindgen/codegen/mod.rs

@@ -728,7 +728,8 @@ impl CodeGenerator for Var {
                     if let Some(cstr) = cstr {
                         let cstr_ty = quote! { ::#prefix::ffi::CStr };
                         if rust_features.literal_cstr &&
-                            options.rust_edition >= RustEdition::Rust2021
+                            options.get_rust_edition() >=
+                                RustEdition::Rust2021
                         {
                             let cstr = proc_macro2::Literal::c_string(&cstr);
                             result.push(quote! {
@@ -3917,12 +3918,11 @@ impl std::str::FromStr for MacroTypeVariation {
 }
 
 /// Enum for the edition of Rust language to use.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Debug, Default)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Debug)]
 pub enum RustEdition {
     /// Rust 2015 language edition
     Rust2015,
     /// Rust 2018 language edition
-    #[default]
     Rust2018,
     /// Rust 2021 language edition
     Rust2021,

bindgen/features.rs

@@ -167,13 +167,15 @@ define_rust_targets! {
     Stable_1_71(71) => { c_unwind_abi: #106075 },
     Stable_1_68(68) => { abi_efiapi: #105795 },
     Stable_1_64(64) => { core_ffi_c: #94503 },
+    Stable_1_56(56) => { edition_2021: #88100 },
     Stable_1_51(51) => { raw_ref_macros: #80886 },
     Stable_1_59(59) => { const_cstr: #54745 },
     Stable_1_47(47) => { larger_arrays: #74060 },
     Stable_1_43(43) => { associated_constants: #68952 },
     Stable_1_40(40) => { non_exhaustive: #44109 },
     Stable_1_36(36) => { maybe_uninit: #60445 },
     Stable_1_33(33) => { repr_packed_n: #57049 },
+    // Stable_1_31(31) => { edition_2018: #54057 },
 }
 
 /// Latest stable release of Rust that is supported by bindgen

bindgen/lib.rs

@@ -531,7 +531,7 @@ impl BindgenOptions {
 
     /// Update rust edition version
     pub fn set_rust_edition(&mut self, rust_edition: RustEdition) {
-        self.rust_edition = rust_edition;
+        self.rust_edition = Some(rust_edition);
     }
 
     /// Update rust target version

bindgen/options/cli.rs

@@ -19,13 +19,6 @@ use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::{fs::File, process::exit};
 
-fn rust_edition_help() -> String {
-    format!(
-        "Version of the Rust language edition. Defaults to {}.",
-        RustEdition::default()
-    )
-}
-
 fn rust_target_help() -> String {
     format!(
         "Version of the Rust compiler to target. Any Rust version after {EARLIEST_STABLE_RUST} is supported. Defaults to {}.",
@@ -339,7 +332,8 @@ struct BindgenCommand {
     /// Add a RAW_LINE of Rust code to a given module with name MODULE_NAME.
     #[arg(long, number_of_values = 2, value_names = ["MODULE_NAME", "RAW_LINE"])]
     module_raw_line: Vec<String>,
-    #[arg(long, help = rust_edition_help())]
+    /// Version of the Rust language edition. Defaults to 2018 if used from CLI, unless target version does not support it. Defaults to current crate's edition if used from API.
+    #[arg(long)]
     rust_edition: Option<RustEdition>,
     #[arg(long, help = rust_target_help())]
     rust_target: Option<RustTarget>,

bindgen/options/mod.rs

@@ -1595,8 +1595,7 @@ options! {
         as_args: |value, args| (!value).as_args(args, "--no-prepend-enum-name"),
     },
     /// Version of the Rust compiler to target.
-    rust_edition: RustEdition {
-        default: RustEdition::default(),
+    rust_edition: Option<RustEdition> {
         methods: {
             /// Specify the Rust edition version.
             ///
@@ -1607,8 +1606,10 @@ options! {
             }
         },
         as_args: |rust_edition, args| {
-            args.push("--rust-edition".to_owned());
-            args.push(rust_edition.to_string());
+            if let Some(rust_edition) = rust_edition {
+                args.push("--rust-edition".to_owned());
+                args.push(rust_edition.to_string());
+            }
         },
     },
     /// Version of the Rust compiler to target.
@@ -2168,3 +2169,17 @@ options! {
         as_args: "--clang-macro-fallback-build-dir",
     }
 }
+
+impl BindgenOptions {
+    /// Get default Rust edition, unless it is set by the user
+    pub fn get_rust_edition(&self) -> RustEdition {
+        self.rust_edition.unwrap_or_else(|| {
+            if !self.rust_features.edition_2021 {
+                RustEdition::Rust2018
+            } else {
+                // For now, we default to 2018, but this might need to be rethought
+                RustEdition::Rust2018
+            }
+        })
+    }
+}