extract main NLL MIR dump function

this will allow calling from polonius MIR

compiler/rustc_borrowck/src/nll.rs

@@ -232,6 +232,33 @@ pub(super) fn dump_nll_mir<'tcx>(
         &0,
         body,
         |pass_where, out| {
+            emit_nll_mir(tcx, regioncx, closure_region_requirements, borrow_set, pass_where, out)
+        },
+        options,
+    );
+
+    // Also dump the region constraint graph as a graphviz file.
+    let _: io::Result<()> = try {
+        let mut file = create_dump_file(tcx, "regioncx.all.dot", false, "nll", &0, body)?;
+        regioncx.dump_graphviz_raw_constraints(&mut file)?;
+    };
+
+    // Also dump the region constraint SCC graph as a graphviz file.
+    let _: io::Result<()> = try {
+        let mut file = create_dump_file(tcx, "regioncx.scc.dot", false, "nll", &0, body)?;
+        regioncx.dump_graphviz_scc_constraints(&mut file)?;
+    };
+}
+
+/// Produces the actual NLL MIR sections to emit during the dumping process.
+pub(crate) fn emit_nll_mir<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    regioncx: &RegionInferenceContext<'tcx>,
+    closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
+    borrow_set: &BorrowSet<'tcx>,
+    pass_where: PassWhere,
+    out: &mut dyn io::Write,
+) -> io::Result<()> {
     match pass_where {
         // Before the CFG, dump out the values for each region variable.
         PassWhere::BeforeCFG => {
@@ -266,21 +293,6 @@ pub(super) fn dump_nll_mir<'tcx>(
         PassWhere::BeforeBlock(_) | PassWhere::AfterLocation(_) | PassWhere::AfterCFG => {}
     }
     Ok(())
-        },
-        options,
-    );
-
-    // Also dump the region constraint graph as a graphviz file.
-    let _: io::Result<()> = try {
-        let mut file = create_dump_file(tcx, "regioncx.all.dot", false, "nll", &0, body)?;
-        regioncx.dump_graphviz_raw_constraints(&mut file)?;
-    };
-
-    // Also dump the region constraint SCC graph as a graphviz file.
-    let _: io::Result<()> = try {
-        let mut file = create_dump_file(tcx, "regioncx.scc.dot", false, "nll", &0, body)?;
-        regioncx.dump_graphviz_scc_constraints(&mut file)?;
-    };
 }
 
 #[allow(rustc::diagnostic_outside_of_impl)]

compiler/rustc_middle/src/mir/pretty.rs

@@ -23,6 +23,7 @@ pub(crate) const ALIGN: usize = 40;
 
 /// An indication of where we are in the control flow graph. Used for printing
 /// extra information in `dump_mir`
+#[derive(Clone)]
 pub enum PassWhere {
     /// We have not started dumping the control flow graph, but we are about to.
     BeforeCFG,