rustc_metadata: move comment closer to code

This was added in cc3c8bb when it was
closer to the `extract_one` call. Move it back near that call.

Author: tamird

compiler/rustc_metadata/src/locator.rs

@@ -499,8 +499,11 @@ impl<'a> CrateLocator<'a> {
 dylibs:FxIndexMap<PathBuf,PathKind>,
 ) -> Result<Option<(Svh,Library)>,CrateError>{
 letmut slot = None;
-// Order here matters, rmeta should come first. See comment in
-// `extract_one` below.
+// Order here matters, rmeta should come first.
+//
+// Make sure there's at most one rlib and at most one dylib.
+//
+// See comment in `extract_one` below.
 let source = CrateSource{
 rmeta:self.extract_one(rmetas,CrateFlavor::Rmeta,&mut slot)?,
 rlib:self.extract_one(rlibs,CrateFlavor::Rlib,&mut slot)?,
@@ -729,7 +732,6 @@ impl<'a> CrateLocator<'a> {
  || file.starts_with(self.target.dll_prefix.as_ref())
  && file.ends_with(self.target.dll_suffix.as_ref())
 {
-// Make sure there's at most one rlib and at most one dylib.
 // Note to take care and match against the non-canonicalized name:
 // some systems save build artifacts into content-addressed stores
 // that do not preserve extensions, and then link to them using