Merge #2217

2217: Implement FromStr for enum Edition r=matklad a=clemarescx

Just did this as I came across the comment in the code asking for implementing `std::str::FromStr` for `input::Edition`.
Not sure what was meant by "proper error handling" though, `panic!` with a descriptive message might not be it 😅 

Co-authored-by: Metabaron <metabaron@tuta.io>

crates/ra_db/src/fixture.rs

@@ -1,5 +1,6 @@
 //! FIXME: write short doc here
 
+use std::str::FromStr;
 use std::sync::Arc;
 
 use ra_cfg::CfgOptions;
@@ -164,7 +165,7 @@ fn parse_meta(meta: &str) -> ParsedMeta {
         match key {
             "crate" => krate = Some(value.to_string()),
             "deps" => deps = value.split(',').map(|it| it.to_string()).collect(),
-            "edition" => edition = Edition::from_string(&value),
+            "edition" => edition = Edition::from_str(&value).unwrap(),
             "cfg" => {
                 for key in value.split(',') {
                     match split1(key, '=') {

crates/ra_db/src/input.rs

@@ -13,6 +13,7 @@ use ra_syntax::SmolStr;
 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
@@ -97,12 +98,18 @@ pub enum Edition {
     Edition2015,
 }
 
-impl Edition {
-    //FIXME: replace with FromStr with proper error handling
-    pub fn from_string(s: &str) -> Edition {
+#[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" => Edition::Edition2015,
-            "2018" | _ => Edition::Edition2018,
+            "2015" => Ok(Edition::Edition2015),
+            "2018" => Ok(Edition::Edition2018),
+            _ => Err(ParseEditionError { msg: format!("unknown edition: {}", s) }),
         }
     }
 }

crates/ra_project_model/src/cargo_workspace.rs

@@ -1,6 +1,7 @@
 //! 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};
@@ -140,18 +141,21 @@ impl CargoWorkspace {
         let ws_members = &meta.workspace_members;
 
         for meta_pkg in meta.packages {
-            let is_member = ws_members.contains(&meta_pkg.id);
+            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 pkg = packages.alloc(PackageData {
-                name: meta_pkg.name,
-                manifest: meta_pkg.manifest_path.clone(),
+                name,
+                manifest: manifest_path,
                 targets: Vec::new(),
                 is_member,
-                edition: Edition::from_string(&meta_pkg.edition),
+                edition,
                 dependencies: Vec::new(),
                 features: Vec::new(),
             });
             let pkg_data = &mut packages[pkg];
-            pkg_by_id.insert(meta_pkg.id.clone(), pkg);
+            pkg_by_id.insert(id, pkg);
             for meta_tgt in meta_pkg.targets {
                 let tgt = targets.alloc(TargetData {
                     pkg,