Auto merge of #60984 - matthewjasper:borrowck-error-reporting-cleanup, r=pnkfelix

Borrowck error reporting cleanup

* Don't show variables created by desugarings in borrowck errors
* Move "conflict error" reporting to it's own module, so that `error_reporting` contains only common error reporting methods.
* Remove unused `ScopeTree` parameter.

r? @pnkfelix

Author: bors

src/librustc/mir/mod.rs

@@ -915,6 +915,13 @@ impl<'tcx> LocalDecl<'tcx> {
         }
     }
 
+    /// Returns `true` is the local is from a compiler desugaring, e.g.,
+    /// `__next` from a `for` loop.
+    #[inline]
+    pub fn from_compiler_desugaring(&self) -> bool {
+        self.source_info.span.compiler_desugaring_kind().is_some()
+    }
+
     /// Creates a new `LocalDecl` for a temporary.
     #[inline]
     pub fn new_temp(ty: Ty<'tcx>, span: Span) -> Self {