Keep inlined var_debug_info only when full debug info is used

Author: kornelski

compiler/rustc_mir_transform/src/inline.rs

@@ -987,9 +987,10 @@ fn inline_call<'tcx, I: Inliner<'tcx>>(
         .opts
         .unstable_opts
         .inline_mir_preserve_debug
-        .unwrap_or(tcx.sess.opts.debuginfo != DebugInfo::None)
+        // only "full" promises any variable-level information
+        .unwrap_or(self.opts.debuginfo == DebugInfo::Full)
     {
-        // Note that we need to preserve these in the standard library so that
+        // -Zinline-mir-preserve-debug is enabled when building the standard library, so that
         // people working on rust can build with or without debuginfo while
         // still getting consistent results from the mir-opt tests.
         caller_body.var_debug_info.append(&mut callee_body.var_debug_info);