proc_macro: don't expose compiler-internal FileName in public API.

src/libproc_macro/lib.rs

@@ -50,6 +50,7 @@ mod diagnostic;
 pub use diagnostic::{Diagnostic, Level};
 
 use std::{ascii, fmt, iter};
+use std::path::PathBuf;
 use rustc_data_structures::sync::Lrc;
 use std::str::FromStr;
 
@@ -421,8 +422,11 @@ impl SourceFile {
     ///
     /// [`is_real`]: #method.is_real
     #[unstable(feature = "proc_macro_span", issue = "38356")]
-    pub fn path(&self) -> &FileName {
-        &self.filemap.name
+    pub fn path(&self) -> PathBuf {
+        match self.filemap.name {
+            FileName::Real(ref path) => path.clone(),
+            _ => PathBuf::from(self.filemap.name.to_string())
+        }
     }
 
     /// Returns `true` if this source file is a real source file, and not generated by an external
@@ -436,18 +440,12 @@ impl SourceFile {
     }
 }
 
-#[unstable(feature = "proc_macro_span", issue = "38356")]
-impl AsRef<FileName> for SourceFile {
-    fn as_ref(&self) -> &FileName {
-        self.path()
-    }
-}
 
 #[unstable(feature = "proc_macro_span", issue = "38356")]
 impl fmt::Debug for SourceFile {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_struct("SourceFile")
-            .field("path", self.path())
+            .field("path", &self.path())
             .field("is_real", &self.is_real())
             .finish()
     }
@@ -463,13 +461,6 @@ impl PartialEq for SourceFile {
 #[unstable(feature = "proc_macro_span", issue = "38356")]
 impl Eq for SourceFile {}
 
-#[unstable(feature = "proc_macro_span", issue = "38356")]
-impl PartialEq<FileName> for SourceFile {
-    fn eq(&self, other: &FileName) -> bool {
-        self.as_ref() == other
-    }
-}
-
 /// A single token or a delimited sequence of token trees (e.g. `[1, (), ..]`).
 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 #[derive(Clone)]