Cleanup proc_macro config

In general, there should be no reason to call `.to_string_lossy`.
If you want to display the path, use `.display()`.
If you want to pass the path to an OS API (like std::process::Command)
than use `PathBuf` or `OsString`.

crates/rust-analyzer/src/config.rs

@@ -7,6 +7,8 @@
 //! configure the server itself, feature flags are passed into analysis, and
 //! tweak things like automatic insertion of `()` in completions.
 
+use std::{ffi::OsString, path::PathBuf};
+
 use lsp_types::TextDocumentClientCapabilities;
 use ra_flycheck::FlycheckConfig;
 use ra_ide::{CompletionConfig, InlayHintsConfig};
@@ -20,7 +22,7 @@ pub struct Config {
     pub with_sysroot: bool,
     pub publish_diagnostics: bool,
     pub lru_capacity: Option<usize>,
-    pub proc_macro_srv: Option<(String, Vec<String>)>,
+    pub proc_macro_srv: Option<(PathBuf, Vec<OsString>)>,
     pub files: FilesConfig,
     pub notifications: NotificationsConfig,
 
@@ -135,7 +137,7 @@ impl Config {
         match get(value, "/procMacro/enable") {
             Some(true) => {
                 if let Ok(path) = std::env::current_exe() {
-                    self.proc_macro_srv = Some((path.to_string_lossy().to_string(), vec!["proc-macro".to_string()]));
+                    self.proc_macro_srv = Some((path, vec!["proc-macro".into()]));
                 }
             }
             _ => self.proc_macro_srv = None,

crates/rust-analyzer/src/world.rs

@@ -153,7 +153,7 @@ impl WorldState {
                 Err(err) => {
                     log::error!(
                         "Failed to run ra_proc_macro_srv from path {}, error: {:?}",
-                        path,
+                        path.display(),
                         err
                     );
                     ProcMacroClient::dummy()