2 files changed, 29 insertions, 21 deletions

diff --git a/crates/ra_db/src/input.rs b/crates/ra_db/src/input.rs
index 0015d6b5e..777e63442 100644
--- a/crates/ra_db/src/input.rs
+++ b/crates/ra_db/src/input.rs
@@ -6,14 +6,14 @@
 //! actual IO. See `vfs` and `project_model` in the `ra_lsp_server` crate for how
 //! actual IO is done and lowered to input.
 
-use rustc_hash::FxHashMap;
+use std::{fmt, str::FromStr};
 
 use ra_cfg::CfgOptions;
 use ra_syntax::SmolStr;
+use rustc_hash::FxHashMap;
 use rustc_hash::FxHashSet;
 
 use crate::{RelativePath, RelativePathBuf};
-use std::str::FromStr;
 
 /// `FileId` is an integer which uniquely identifies a file. File paths are
 /// messy and system-dependent, so most of the code should work directly with
@@ -98,22 +98,6 @@ pub enum Edition {
     Edition2015,
 }
 
-#[derive(Debug)]
-pub struct ParseEditionError {
-    pub msg: String,
-}
-
-impl FromStr for Edition {
-    type Err = ParseEditionError;
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "2015" => Ok(Edition::Edition2015),
-            "2018" => Ok(Edition::Edition2018),
-            _ => Err(ParseEditionError { msg: format!("unknown edition: {}", s) }),
-        }
-    }
-}
-
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
 pub struct Env {
     entries: FxHashMap<String, String>,
@@ -247,6 +231,32 @@ impl CrateGraph {
     }
 }
 
+#[derive(Debug)]
+pub struct ParseEditionError {
+    invalid_input: String,
+}
+
+impl FromStr for Edition {
+    type Err = ParseEditionError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let res = match s {
+            "2015" => Edition::Edition2015,
+            "2018" => Edition::Edition2018,
+            _ => Err(ParseEditionError { invalid_input: s.to_string() })?,
+        };
+        Ok(res)
+    }
+}
+
+impl fmt::Display for ParseEditionError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "invalid edition: {:?}", self.invalid_input)
+    }
+}
+
+impl std::error::Error for ParseEditionError {}
+
 #[cfg(test)]
 mod tests {
     use super::{CfgOptions, CrateGraph, Edition::Edition2018, Env, FileId, SmolStr};
diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index cf88911b7..c128e608d 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -1,7 +1,6 @@
 //! FIXME: write short doc here
 
 use std::path::{Path, PathBuf};
-use std::str::FromStr;
 
 use cargo_metadata::{CargoOpt, MetadataCommand};
 use ra_arena::{impl_arena_id, Arena, RawId};
@@ -143,8 +142,7 @@ impl CargoWorkspace {
         for meta_pkg in meta.packages {
             let cargo_metadata::Package { id, edition, name, manifest_path, .. } = meta_pkg;
             let is_member = ws_members.contains(&id);
-            let edition = Edition::from_str(&edition)
-                .map_err(|e| (format!("metadata for package {} failed: {}", &name, e.msg)))?;
+            let edition = edition.parse::<Edition>()?;
             let pkg = packages.alloc(PackageData {
                 name,
                 manifest: manifest_path,