rustc_driver: add -Z pretty-keep-going to continue compilation after pretty-printing.

Author: eddyb

src/librustc/session/config.rs

@@ -580,6 +580,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "Include assignment analysis data in --pretty flowgraph output"),
     flowgraph_print_all: bool = (false, parse_bool,
         "Include all dataflow analysis data in --pretty flowgraph output"),
+    pretty_keep_going: bool = (false, parse_bool,
+        "Do not stop after pretty-printing (use with --pretty)"),
     print_region_graph: bool = (false, parse_bool,
          "Prints region inference graph. \
           Use with RUST_REGION_GRAPH=help for more info"),

src/librustc_driver/lib.rs

@@ -342,7 +342,10 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
                 let output = state.output;
                 pretty::print_from_phase(state, ppm, opt_uii.as_ref(), output).unwrap();
             };
-            phase.stop = Compilation::Stop;
+
+            if !sess.opts.debugging_opts.pretty_keep_going {
+                phase.stop = Compilation::Stop;
+            }
         }
 
         if self.save_analysis {