WIP Trying to investiate issue rust-lang#10031. Adding mucho debug instrumentation.

modmin.rs:
    #[crate_id = "min#0.1"];

    #[cfg(not(nontuple))]
    pub struct Wrap<A>(A);

    #[cfg(nontuple)]
    pub struct Wrap<A>{ a: A }

    #[cfg(nontuple)]
    pub fn Wrap<A>(a: A) -> Wrap<A> { Wrap{ a: a } }

test.rs:
    extern mod min;

    fn main() {
        let _x: min::Wrap<()> = min::Wrap(());
    }

Makefile:
    default: test

    RUSTC=rustc

    TEMP_FILE=$(mktmp -t deps)
    TEMP_FILE=/tmp/foo

    define DEPS_ON_RUSTC
    # $(1) rustc args
    # $(2) output variable
      $(2) = $(shell TMP=$(TEMP_FILE) $(RUSTC) --dep-info $TMP --no-analysis $(1) ; sed -e s'/^[^:]*://' $TMP )
    endef

    define FILENAME_ON_RUSTC
    # $(1) rustc args
    # $(2) output variable
       $(2) := $(shell $(RUSTC) --crate-file-name $(1))
    endef

    LIBMOD_FLAGS=--lib modmin.rs
    $(eval $(call FILENAME_ON_RUSTC, $(LIBMOD_FLAGS), LIBMOD))
    $(eval $(call DEPS_ON_RUSTC, $(LIBMOD_FLAGS), LIBMOD_DEPS))
    $(LIBMOD): $(LIBMOD_DEPS)
    	$(RUSTC) $(LIBMOD_FLAGS)

    TEST_FLAGS=--test test.rs
    $(eval $(call FILENAME_ON_RUSTC, $(TEST_FLAGS), TEST))
    $(eval $(call DEPS_ON_RUSTC, $(TEST_FLAGS), TEST_DEPS))
    $(TEST): $(TEST_DEPS) $(LIBMOD)
    	$(RUSTC) -L. $(TEST_FLAGS)

    clean:
    	rm -f $(LIBMOD) $(TEST)

Author: pnkfelix

src/librustc/middle/astencode.rs

@@ -1377,7 +1377,7 @@ fn decode_side_tables(xcx: @ExtendedDecodeContext,
                         let mut ty_param_defs = dcx.tcx
                                                    .ty_param_defs
                                                    .borrow_mut();
-                        ty_param_defs.get().insert(id, bounds);
+                        ty_param_defs.get().insert(id, bounds); // XXX
                     }
                     c::tag_table_method_map => {
                         let entry = val_dsr.read_method_map_entry(xcx);

src/librustc/middle/typeck/check/mod.rs

@@ -3819,7 +3819,8 @@ pub fn instantiate_path(fcx: @FnCtxt,
         ty_substs_len += segment.types.len()
     }
 
-    debug!("tpt={} ty_param_count={:?} ty_substs_len={:?}",
+    debug!("pth={} tpt={} ty_param_count={:?} ty_substs_len={:?}",
+           pth.repr(fcx.tcx()),
            tpt.repr(fcx.tcx()),
            ty_param_count,
            ty_substs_len);

src/librustc/middle/typeck/collect.rs

@@ -966,7 +966,7 @@ pub fn ty_generics(ccx: &CrateCtxt,
                     let mut ty_param_defs = ccx.tcx
                                                .ty_param_defs
                                                .borrow_mut();
-                    ty_param_defs.get().insert(param.id, def);
+                    ty_param_defs.get().insert(param.id, def); // XXX
                     def
                 }
             }

src/librustc/util/ppaux.rs

@@ -478,7 +478,7 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
               Some(def) => cx.sess.str_of(def.ident).to_owned(),
               None => {
                   // This should not happen...
-                  format!("BUG[{:?}]", id)
+                  format!("BUG[{:?};({},{})]", id, did.crate, did.node)
               }
           };
           if !cx.sess.verbose() { ident } else { format!("{}:{:?}", ident, did) }
@@ -686,6 +686,23 @@ impl Repr for ast::Pat {
     }
 }
 
+impl Repr for ast::Path {
+    fn repr(&self, tcx: ctxt) -> ~str {
+        format!("Path({}, {})",
+                if self.global { "global" } else { "local" },
+                self.segments.repr(tcx))
+    }
+}
+
+impl Repr for ast::PathSegment {
+    fn repr(&self, tcx: ctxt) -> ~str {
+        format!("PathSegment({}, {}, {})",
+                self.identifier.repr(tcx),
+                self.lifetimes.repr(tcx),
+                self.types.repr(tcx))
+    }
+}
+
 impl Repr for ty::BoundRegion {
     fn repr(&self, tcx: ctxt) -> ~str {
         match *self {