internal/core/debug: dereference non-rooted

A related change in the v3 evaluator allows inline
structs to be structure shared. As a consequence,
references may be meaningless, as they have no full
path.

This change does not print a shared address if a
node is not rooted.

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: Id10ce012aa5eb7623ac6c3730d9f4d36d44d27cd
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1202218
Reviewed-by: Matthew Sackman <matthew@cue.works>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

Author: mpvl

cue/testdata/compile/scope.txtar

@@ -113,7 +113,9 @@ Result:
   let B#1 = (struct){
     open: (int){ int }
   }
-  f: ~(B#1)
+  f: (struct){
+    open: (int){ int }
+  }
   schema: (_|_){
     // [structural cycle]
     next: (_|_){
@@ -135,14 +137,7 @@ diff old new
 
  Result:
  (_|_){
-@@ -23,17 +23,14 @@
-   let B#1 = (struct){
-     open: (int){ int }
-   }
--  f: (struct){
--    open: (int){ int }
--  }
-+  f: ~(B#1)
+@@ -29,11 +29,10 @@
    schema: (_|_){
      // [structural cycle]
      next: (_|_){

cue/testdata/eval/let.txtar

@@ -335,8 +335,16 @@ Result:
         "\(〈0;let X#1F〉)": 〈0;let X#1F〉
       }
     }
-    "0": ~(nestedFor.X#1E)
-    "1": ~(nestedFor.X#1E)
+    "0": (struct){
+      let X#1Fmulti = 〈1;x〉
+      "2": (int){ 2 }
+      "1": (int){ 1 }
+    }
+    "1": (struct){
+      let X#1Fmulti = 〈1;x〉
+      "2": (int){ 2 }
+      "1": (int){ 1 }
+    }
   }
   keepDescending: (struct){
     t1: (struct){
@@ -493,26 +501,25 @@ diff old new
      }
    }
    nestedFor: (struct){
-@@ -188,16 +164,8 @@
-         "\(〈0;let X#1F〉)": 〈0;let X#1F〉
-       }
+@@ -190,13 +166,13 @@
      }
--    "0": (struct){
--      let X#1Fmulti = 〈1;x〉
+     "0": (struct){
+       let X#1Fmulti = 〈1;x〉
 -      "1": (int){ 1 }
 -      "2": (int){ 2 }
--    }
--    "1": (struct){
--      let X#1Fmulti = 〈1;x〉
++      "2": (int){ 2 }
++      "1": (int){ 1 }
+     }
+     "1": (struct){
+       let X#1Fmulti = 〈1;x〉
 -      "1": (int){ 1 }
 -      "2": (int){ 2 }
--    }
-+    "0": ~(nestedFor.X#1E)
-+    "1": ~(nestedFor.X#1E)
++      "2": (int){ 2 }
++      "1": (int){ 1 }
+     }
    }
    keepDescending: (struct){
-     t1: (struct){
-@@ -234,8 +202,8 @@
+@@ -234,8 +210,8 @@
        b: (string){ "e" }
      }
      let T#23multi = 〈1;v〉

cue/testdata/references/let.txtar

@@ -442,13 +442,17 @@ Disjuncts:    121
         let x#E = (struct){
           a: (int){ 1 }
         }
-        0: ~(scalarReference.inList.p0.x#E)
+        0: (struct){
+          a: (int){ 1 }
+        }
       }
       p1: (#list){
         let x#F = (struct){
           a: (int){ 1 }
         }
-        0: ~(scalarReference.inList.p1.x#F)
+        0: (struct){
+          a: (int){ 1 }
+        }
       }
     }
   }
@@ -490,26 +494,6 @@ diff old new
          //     ./in.cue:54:17
        }
      }
-@@ -145,17 +145,13 @@
-         let x#E = (struct){
-           a: (int){ 1 }
-         }
--        0: (struct){
--          a: (int){ 1 }
--        }
-+        0: ~(scalarReference.inList.p0.x#E)
-       }
-       p1: (#list){
-         let x#F = (struct){
-           a: (int){ 1 }
-         }
--        0: (struct){
--          a: (int){ 1 }
--        }
-+        0: ~(scalarReference.inList.p1.x#F)
-       }
-     }
-   }
 -- diff/todo/p3 --
 Investigate let divergence. Probably okay.
 -- out/eval --

cue/testdata/resolve/035_excluded_embedding_from_closing.txtar

@@ -93,7 +93,9 @@ Result:
     let B#1 = (#struct){
       open: (int){ int }
     }
-    b: ~(#S.B#1)
+    b: (#struct){
+      open: (int){ int }
+    }
   }
   V: (_|_){
     // [eval]
@@ -139,14 +141,7 @@ diff old new
      ./in.cue:10:5
 
  Result:
-@@ -23,39 +17,31 @@
-     let B#1 = (#struct){
-       open: (int){ int }
-     }
--    b: (#struct){
--      open: (int){ int }
--    }
-+    b: ~(#S.B#1)
+@@ -29,33 +23,27 @@
    }
    V: (_|_){
      // [eval]

internal/core/debug/debug.go

@@ -131,35 +131,36 @@ func (w *printer) shared(v *adt.Vertex) {
 // printShared prints a reference to a structure-shared node that is a value
 // of v, if it is a shared node. It reports the dereferenced node and whether
 // the node was printed.
-func (w *printer) printShared(v *adt.Vertex) (x *adt.Vertex, ok bool) {
+func (w *printer) printShared(v0 *adt.Vertex) (x *adt.Vertex, ok bool) {
+
 	// Handle cyclic shared nodes differently.  If a shared node was part of
 	// a disjunction, it will still be wrapped in a disjunct Vertex.
 	// Similarly, a shared node should never point to a disjunct directly,
 	// but rather to the original arc that subsequently points to a
 	// disjunct.
-	v = v.DerefDisjunct()
-	useReference := v.IsShared
-	isCyclic := v.IsCyclic
-	s, ok := v.BaseValue.(*adt.Vertex)
-	v = v.DerefValue()
-	isCyclic = isCyclic || v.IsCyclic
+	v0 = v0.DerefDisjunct()
+	isCyclic := v0.IsCyclic
+	s, ok := v0.BaseValue.(*adt.Vertex)
+	v1 := v0.DerefValue()
+	useReference := v0.IsShared && v1.Rooted()
+	isCyclic = isCyclic || v1.IsCyclic
 	_ = isCyclic
 	// NOTE(debug): use this line instead of the following to expand shared
 	// cases where it is safe to do so.
 	// if useReference && isCyclic && ok && len(v.Arcs) > 0 {
-	if useReference && ok && len(v.Arcs) > 0 {
-		w.shared(s)
-		return v, true
+	if useReference && ok && len(v1.Arcs) > 0 {
+		w.shared(v1)
+		return v1, true
 	}
-	if !w.pushVertex(v) {
+	if !w.pushVertex(v1) {
 		if s != nil {
 			w.shared(s)
 			w.string(" =>")
 		}
-		w.shared(v)
-		return v, true
+		w.shared(v1)
+		return v1, true
 	}
-	return v, false
+	return v1, false
 }
 
 func (w *printer) pushVertex(v *adt.Vertex) bool {