Merge pull request #372 from dtolnay/stdbacktrace

Access Backtrace exclusively through ::thiserror

Author: dtolnay

build.rs

@@ -5,12 +5,14 @@ use std::io::ErrorKind;
 use std::iter;
 use std::path::Path;
 use std::process::{self, Command, Stdio};
+use std::str;
 
 fn main() {
     println!("cargo:rerun-if-changed=build/probe.rs");
 
     println!("cargo:rustc-check-cfg=cfg(error_generic_member_access)");
     println!("cargo:rustc-check-cfg=cfg(thiserror_nightly_testing)");
+    println!("cargo:rustc-check-cfg=cfg(thiserror_no_backtrace_type)");
 
     let error_generic_member_access;
     let consider_rustc_bootstrap;
@@ -54,6 +56,17 @@ fn main() {
     if consider_rustc_bootstrap {
         println!("cargo:rerun-if-env-changed=RUSTC_BOOTSTRAP");
     }
+
+    let rustc = match rustc_minor_version() {
+        Some(rustc) => rustc,
+        None => return,
+    };
+
+    // std::backtrace::Backtrace stabilized in Rust 1.65
+    // https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html#stabilized-apis
+    if rustc < 65 {
+        println!("cargo:rustc-cfg=thiserror_no_backtrace_type");
+    }
 }
 
 fn compile_probe(rustc_bootstrap: bool) -> bool {
@@ -135,6 +148,17 @@ fn compile_probe(rustc_bootstrap: bool) -> bool {
     success
 }
 
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = cargo_env_var("RUSTC");
+    let output = Command::new(rustc).arg("--version").output().ok()?;
+    let version = str::from_utf8(&output.stdout).ok()?;
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+    pieces.next()?.parse().ok()
+}
+
 fn cargo_env_var(key: &str) -> OsString {
     env::var_os(key).unwrap_or_else(|| {
         eprintln!("Environment variable ${key} is not set during execution of build script");

impl/src/expand.rs

@@ -118,12 +118,12 @@ fn impl_struct(input: Struct) -> TokenStream {
             } else if type_is_option(backtrace_field.ty) {
                 Some(quote! {
                     if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
-                        #request.provide_ref::<::std::backtrace::Backtrace>(backtrace);
+                        #request.provide_ref::<::thiserror::__private::Backtrace>(backtrace);
                     }
                 })
             } else {
                 Some(quote! {
-                    #request.provide_ref::<::std::backtrace::Backtrace>(&self.#backtrace);
+                    #request.provide_ref::<::thiserror::__private::Backtrace>(&self.#backtrace);
                 })
             };
             quote! {
@@ -134,12 +134,12 @@ fn impl_struct(input: Struct) -> TokenStream {
         } else if type_is_option(backtrace_field.ty) {
             quote! {
                 if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
-                    #request.provide_ref::<::std::backtrace::Backtrace>(backtrace);
+                    #request.provide_ref::<::thiserror::__private::Backtrace>(backtrace);
                 }
             }
         } else {
             quote! {
-                #request.provide_ref::<::std::backtrace::Backtrace>(&self.#backtrace);
+                #request.provide_ref::<::thiserror::__private::Backtrace>(&self.#backtrace);
             }
         };
         quote! {
@@ -309,12 +309,12 @@ fn impl_enum(input: Enum) -> TokenStream {
                     let self_provide = if type_is_option(backtrace_field.ty) {
                         quote! {
                             if let ::core::option::Option::Some(backtrace) = backtrace {
-                                #request.provide_ref::<::std::backtrace::Backtrace>(backtrace);
+                                #request.provide_ref::<::thiserror::__private::Backtrace>(backtrace);
                             }
                         }
                     } else {
                         quote! {
-                            #request.provide_ref::<::std::backtrace::Backtrace>(backtrace);
+                            #request.provide_ref::<::thiserror::__private::Backtrace>(backtrace);
                         }
                     };
                     quote! {
@@ -357,12 +357,12 @@ fn impl_enum(input: Enum) -> TokenStream {
                     let body = if type_is_option(backtrace_field.ty) {
                         quote! {
                             if let ::core::option::Option::Some(backtrace) = backtrace {
-                                #request.provide_ref::<::std::backtrace::Backtrace>(backtrace);
+                                #request.provide_ref::<::thiserror::__private::Backtrace>(backtrace);
                             }
                         }
                     } else {
                         quote! {
-                            #request.provide_ref::<::std::backtrace::Backtrace>(backtrace);
+                            #request.provide_ref::<::thiserror::__private::Backtrace>(backtrace);
                         }
                     };
                     quote! {
@@ -532,11 +532,11 @@ fn from_initializer(
         let backtrace_member = &backtrace_field.member;
         if type_is_option(backtrace_field.ty) {
             quote! {
-                #backtrace_member: ::core::option::Option::Some(::std::backtrace::Backtrace::capture()),
+                #backtrace_member: ::core::option::Option::Some(::thiserror::__private::Backtrace::capture()),
             }
         } else {
             quote! {
-                #backtrace_member: ::core::convert::From::from(::std::backtrace::Backtrace::capture()),
+                #backtrace_member: ::core::convert::From::from(::thiserror::__private::Backtrace::capture()),
             }
         }
     });

src/lib.rs

@@ -287,6 +287,9 @@ pub mod __private {
     #[cfg(error_generic_member_access)]
     #[doc(hidden)]
     pub use crate::provide::ThiserrorProvide;
+    #[cfg(not(thiserror_no_backtrace_type))]
+    #[doc(hidden)]
+    pub use std::backtrace::Backtrace;
     #[doc(hidden)]
     pub use std::error::Error;
 }