don't print self symbol's internal index unless gensymed

It's just not useful. It also makes it hard to have tests that probe
internal state, since the interning number is very sensitive.

Dumping the number in the case of gensym is not ideal but will do for
now.

src/libsyntax_pos/symbol.rs

@@ -123,7 +123,12 @@ fn from(string: &'a str) -> Symbol {
 
 impl fmt::Debug for Symbol {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}({})", self, self.0)
+        let is_gensymed = with_interner(|interner| interner.is_gensymed(*self));
+        if is_gensymed {
+            write!(f, "{}({})", self, self.0)
+        } else {
+            write!(f, "{}", self)
+        }
     }
 }
 
@@ -201,6 +206,10 @@ fn gensymed(&mut self, symbol: Symbol) -> Symbol {
         Symbol(!0 - self.gensyms.len() as u32 + 1)
     }
 
+    fn is_gensymed(&mut self, symbol: Symbol) -> bool {
+        symbol.0 as usize >= self.strings.len()
+    }
+
     pub fn get(&self, symbol: Symbol) -> &str {
         match self.strings.get(symbol.0 as usize) {
             Some(ref string) => string,

src/test/ui/nll/closure-requirements/escape-argument-callee.stderr

@@ -18,7 +18,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:9 ~ escape_argument_callee[317d]::test[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's, 't0> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(7666))) mut &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7667))) i32, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0(7668))) i32))
+               for<'r, 's, 't0> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) mut &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) i32, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0)) i32))
            ]
    = note: number of external vids: 1
 

src/test/ui/nll/closure-requirements/escape-argument.stderr

@@ -6,7 +6,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:9 ~ escape_argument[317d]::test[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(8634))) mut &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(8635))) i32, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(8635))) i32))
+               for<'r, 's> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) mut &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) i32, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) i32))
            ]
    = note: number of external vids: 1
 

src/test/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.stderr

@@ -24,7 +24,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:20 ~ propagate_approximated_fail_no_postdom[317d]::supply[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9523))) u32>, std::cell::Cell<&'_#2r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9523))) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(9524))) &'_#3r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9523))) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(9524))) u32>))
+               for<'r, 's> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&'_#2r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) &'_#3r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>))
            ]
    = note: number of external vids: 4
 

src/test/ui/nll/closure-requirements/propagate-approximated-ref.stderr

@@ -16,7 +16,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:18 ~ propagate_approximated_ref[317d]::supply[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's, 't0, 't1, 't2, 't3> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(7696))) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7697))) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0(7698))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1(7699))) &'_#2r u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't2(9524))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7697))) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't3(9525))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1(7699))) u32>))
+               for<'r, 's, 't0, 't1, 't2, 't3> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1)) &'_#2r u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't2)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't3)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1)) u32>))
            ]
    = note: number of external vids: 3
    = note: where '_#1r: '_#2r

src/test/ui/nll/closure-requirements/propagate-approximated-to-empty.stderr

@@ -24,7 +24,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:18 ~ propagate_approximated_to_empty[317d]::supply[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's, 't0, 't1, 't2> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(7695))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7696))) &'_#1r u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0(7697))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1(9522))) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't2(9523))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7696))) u32>))
+               for<'r, 's, 't0, 't1, 't2> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) &'_#1r u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1)) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't2)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>))
            ]
    = note: number of external vids: 2
 

src/test/ui/nll/closure-requirements/propagate-approximated-to-static.stderr

@@ -16,7 +16,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:18 ~ propagate_approximated_to_static[317d]::supply[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's, 't0, 't1, 't2> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(7695))) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7696))) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0(7697))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(7696))) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1(9522))) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't2(9523))) u32>))
+               for<'r, 's, 't0, 't1, 't2> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't0)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't1)) std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 't2)) u32>))
            ]
    = note: number of external vids: 2
    = note: where '_#1r: '_#0r

src/test/ui/nll/closure-requirements/propagate-approximated-val.stderr

@@ -16,7 +16,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:18 ~ propagate_approximated_val[317d]::test[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9519))) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(9520))) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9519))) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(9520))) u32>))
+               for<'r, 's> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>))
            ]
    = note: number of external vids: 3
    = note: where '_#1r: '_#2r

src/test/ui/nll/closure-requirements/propagate-despite-same-free-region.stderr

@@ -16,7 +16,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:16 ~ propagate_despite_same_free_region[317d]::supply[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9518))) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(9519))) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(9518))) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(9519))) u32>))
+               for<'r, 's> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) u32>))
            ]
    = note: number of external vids: 3
    = note: where '_#1r: '_#2r

src/test/ui/nll/closure-requirements/return-wrong-bound-region.stderr

@@ -18,7 +18,7 @@ note: External requirements
    |
    = note: defining type: DefId(0/1:9 ~ return_wrong_bound_region[317d]::test[0]::{{closure}}[0]) with closure substs [
                i16,
-               for<'r, 's> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(7661))) i32, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's(8630))) i32)) -> &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r(7661))) i32
+               for<'r, 's> extern "rust-call" fn((&ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) i32, &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 's)) i32)) -> &ReLateBound(DebruijnIndex { depth: 1 }, BrNamed(crate0:DefIndex(0:0), 'r)) i32
            ]
    = note: number of external vids: 1