Allow yeeting context selectors to generate errors

.cirrus.yml

@@ -165,6 +165,10 @@ nightly_test_task:
     - cd compatibility-tests/backtrace-provider-api/
     - rustc --version
     - cargo test
+  yeet_selectors_test_script:
+    - cd compatibility-tests/yeet-selectors/
+    - rustc --version
+    - cargo test
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
 unstable_std_backtraces_test_task:

compatibility-tests/yeet-selectors/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "yeet-selectors"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+snafu = { path = "../.." }

compatibility-tests/yeet-selectors/rust-toolchain

@@ -0,0 +1 @@
+nightly

compatibility-tests/yeet-selectors/src/lib.rs

@@ -0,0 +1,20 @@
+#![feature(yeet_expr)]
+#![cfg(test)]
+
+use snafu::prelude::*;
+
+#[test]
+fn can_yeet_context_selector() {
+    #[derive(Debug, Snafu)]
+    struct MyError {
+        name: String,
+    }
+
+    fn usage() -> Result<(), MyError> {
+        let name = "gronk";
+        do yeet MySnafu { name };
+    }
+
+    let r = usage();
+    assert!(r.is_err(), "{r:?} should have been an error");
+}

snafu-derive/src/shared.rs

@@ -294,6 +294,16 @@ pub mod context_selector {
                         ::core::result::Result::Err(self.build())
                     }
                 }
+
+                impl<#(#original_generics_without_defaults,)* #(#user_field_generics,)*> ::core::convert::From<#parameterized_selector_name> for #parameterized_error_name
+                where
+                    #(#extended_where_clauses),*
+                {
+                    #[track_caller]
+                    fn from(other: #parameterized_selector_name) -> Self {
+                        other.build()
+                    }
+                }
             }
         }
 

tests/build-leaf-error.rs

@@ -22,3 +22,9 @@ fn implements_error() {
 
     map_result().unwrap_err();
 }
+
+#[test]
+fn build_via_from_and_into() {
+    let _e = Error::from(MineSnafu);
+    let _e: Error = MineSnafu.into();
+}