internal/core/adt: partial revert of fixes for 3919

We removed a piece of code which seemingly
was redundant after the fix for 3919. It turns
out, though, that it is still necessary in some
cases. Reverting it did not affect the results
of 3919 except one change in an error message,
which is now what it was before the change
for 3919.

Issue #3919
Fixes #3931

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I4d8657e3b3c85ab67e60684d3726c6f819e296f3
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1215499
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl

cue/testdata/eval/comprehensions.txtar

@@ -271,9 +271,8 @@ Result:
             // [eval] issue3691.structuralCycle.a.b.c: conflicting values string and {[string]:X} (mismatched types string and struct):
             //     ./issue3691.cue:14:15
             //     ./issue3691.cue:15:5
-            b*: (_|_){// [e]if true {
-              //   c: 〈3;a〉
-              // }[e] & 〈1;X〉
+            b: (_|_){
+              // [cycle] cycle error
             }
           }
         }
@@ -308,20 +307,18 @@ diff old new
              //     ./issue3691.cue:8:10
            }
          }
-@@ -145,13 +140,9 @@
+@@ -145,13 +140,8 @@
              // [eval] issue3691.structuralCycle.a.b.c: conflicting values string and {[string]:X} (mismatched types string and struct):
              //     ./issue3691.cue:14:15
              //     ./issue3691.cue:15:5
 -            //     ./issue3691.cue:17:3
 -            //     ./issue3691.cue:18:10
--            b: (_|_){
+             b: (_|_){
 -              // [structural cycle]
 -              c: (_|_){
 -                // [structural cycle] issue3691.structuralCycle.a.b.c.b.c: structural cycle
 -              }
-+            b*: (_|_){// [e]if true {
-+              //   c: 〈3;a〉
-+              // }[e] & 〈1;X〉
++              // [cycle] cycle error
              }
            }
          }

cue/testdata/eval/issue3919.txtar

@@ -64,13 +64,7 @@ Unifications: 47
 Conjuncts:    73
 Disjuncts:    54
 -- out/evalalpha --
-Errors:
-issue3931.full.bar.bar1.spec.selector: adding field expr not allowed as field set was already referenced:
-    ./let.cue:8:14
-
-Result:
-(_|_){
-  // [eval]
+(struct){
   full: (struct){
     out: (struct){
       env: (struct){
@@ -83,19 +77,15 @@ Result:
     a: (int){ 30080 }
     port: (int){ |(*(int){ 30080 }, (int){ int }) }
   }
-  issue3931: (_|_){
-    // [eval]
-    full: (_|_){
-      // [eval]
-      bar: (_|_){
-        // [eval]
-        bar1: (_|_){
-          // [eval]
-          spec: (_|_){
-            // [eval]
-            selector: (_|_){
-              // [eval] issue3931.full.bar.bar1.spec.selector: adding field expr not allowed as field set was already referenced:
-              //     ./let.cue:8:14
+  issue3931: (struct){
+    full: (struct){
+      bar: (struct){
+        bar1: (struct){
+          spec: (struct){
+            selector: (struct){
+              label: (string){ "foo" }
+              expr?: (list){
+              }
             }
           }
         }
@@ -156,48 +146,7 @@ Result:
 diff old new
 --- old
 +++ new
-@@ -1,4 +1,10 @@
--(struct){
-+Errors:
-+issue3931.full.bar.bar1.spec.selector: adding field expr not allowed as field set was already referenced:
-+    ./let.cue:8:14
-+
-+Result:
-+(_|_){
-+  // [eval]
-   full: (struct){
-     out: (struct){
-       env: (struct){
-@@ -11,15 +17,19 @@
-     a: (int){ 30080 }
-     port: (int){ |(*(int){ 30080 }, (int){ int }) }
-   }
--  issue3931: (struct){
--    full: (struct){
--      bar: (struct){
--        bar1: (struct){
--          spec: (struct){
--            selector: (struct){
--              label: (string){ "foo" }
--              expr?: (list){
--              }
-+  issue3931: (_|_){
-+    // [eval]
-+    full: (_|_){
-+      // [eval]
-+      bar: (_|_){
-+        // [eval]
-+        bar1: (_|_){
-+          // [eval]
-+          spec: (_|_){
-+            // [eval]
-+            selector: (_|_){
-+              // [eval] issue3931.full.bar.bar1.spec.selector: adding field expr not allowed as field set was already referenced:
-+              //     ./let.cue:8:14
-             }
-           }
-         }
-@@ -45,10 +55,7 @@
+@@ -45,10 +45,7 @@
      foo: (struct){
        fooData: (struct){
          total: (struct){
@@ -209,7 +158,7 @@ diff old new
          }
          _hidden: (struct){
            extra: (struct){
-@@ -56,12 +63,7 @@
+@@ -56,12 +53,7 @@
          }
        }
        shared: (struct){

internal/core/adt/unify.go

@@ -215,6 +215,11 @@ func (v *Vertex) unify(c *OpContext, needs condition, mode runMode, checkTypos b
 		// forcefully do an early recursive evaluation to decide the state
 		// of the arc. See https://cuelang.org/issue/3621.
 		n.process(pendingKnown, yield)
+		if n.node.ArcType == ArcPending {
+			for _, a := range n.node.Arcs {
+				a.unify(c, needs, attemptOnly, checkTypos)
+			}
+		}
 		n.completePending(yield)
 	}