make -Z mir-include-spans an optional bool

this allows priority for the CLI even in NLL MIR dumps where we want
this to be true by default, compared to the other passes where it's
mostly off by default

Author: lqd

compiler/rustc_interface/src/tests.rs

@@ -705,7 +705,7 @@ fn test_unstable_options_tracking_hash() {
     untracked!(ls, vec!["all".to_owned()]);
     untracked!(macro_backtrace, true);
     untracked!(meta_stats, true);
-    untracked!(mir_include_spans, true);
+    untracked!(mir_include_spans, Some(true));
     untracked!(nll_facts, true);
     untracked!(no_analysis, true);
     untracked!(no_leak_check, true);

compiler/rustc_middle/src/mir/pretty.rs

@@ -48,13 +48,25 @@ pub enum PassWhere {
 #[derive(Copy, Clone)]
 pub struct PrettyPrintMirOptions {
     /// Whether to include extra comments, like span info. From `-Z mir-include-spans`.
-    pub include_extra_comments: bool,
+    include_extra_comments: bool,
 }
 
 impl PrettyPrintMirOptions {
     /// Create the default set of MIR pretty-printing options from the CLI flags.
     pub fn from_cli(tcx: TyCtxt<'_>) -> Self {
-        Self { include_extra_comments: tcx.sess.opts.unstable_opts.mir_include_spans }
+        // We include extra comments only if there's an explicit opt-in, we don't show them by
+        // default.
+        Self::from_cli_with_default(tcx, false)
+    }
+
+    /// Create MIR pretty-printing options from the CLI flags if specified, using a default value
+    /// otherwise.
+    pub fn from_cli_with_default(tcx: TyCtxt<'_>, include_extra_comments_default: bool) -> Self {
+        // We include extra comments only if there's an explicit opt-in, we don't show them by
+        // default.
+        let include_extra_comments =
+            tcx.sess.opts.unstable_opts.mir_include_spans.unwrap_or(include_extra_comments_default);
+        Self { include_extra_comments }
     }
 }
 

compiler/rustc_session/src/options.rs

@@ -1832,7 +1832,7 @@ options! {
         specified passes to be enabled, overriding all other checks. In particular, this will \
         enable unsound (known-buggy and hence usually disabled) passes without further warning! \
         Passes that are not specified are enabled or disabled by other flags as usual."),
-    mir_include_spans: bool = (false, parse_bool, [UNTRACKED],
+    mir_include_spans: Option<bool> = (None, parse_opt_bool, [UNTRACKED],
         "use line numbers relative to the function in mir pretty printing"),
     mir_keep_place_mention: bool = (false, parse_bool, [TRACKED],
         "keep place mention MIR statements, interpreted e.g., by miri; implies -Zmir-opt-level=0 \