internal/core/adt: fix pointer comparison issue in equalTerminal

This fixes a good ole do not pass a nil pointer of a concrete
value to an interface argument bug.

Fixes #3194

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: Ib16cb8667fe56754b03a9dc3c75fdc363c9abd2b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1196094
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cue/testdata/definitions/hidden.txtar

@@ -104,7 +104,7 @@ diff old new
 -    ./in.cue:6:9
 -    ./in.cue:13:13
      ./in.cue:16:9
-
+ 
  Result:
 @@ -13,9 +11,6 @@
      }

cue/testdata/eval/v0.7.txtar

@@ -204,16 +204,26 @@ mutual: t4: ok: {
 	check: p1 & p2 & p3 & p4 & p5
 }
 
+-- equality.cue --
+issue3194: reduced: {
+	A: *0 | >10
+	A: *0 | >10
+	{
+		out: close({ b: A })
+		out: b: A
+	}.out
+}
+
 -- out/eval/stats --
-Leaks:  0
-Freed:  261
-Reused: 249
-Allocs: 12
-Retain: 166
+Leaks:  4
+Freed:  285
+Reused: 273
+Allocs: 16
+Retain: 170
 
-Unifications: 261
-Conjuncts:    1578
-Disjuncts:    408
+Unifications: 269
+Conjuncts:    1619
+Disjuncts:    436
 -- out/eval --
 Errors:
 definition.t0.err.d1.env.c: field not allowed:
@@ -377,6 +387,12 @@ Result:
       }
     }
   }
+  issue3194: (struct){
+    reduced: (#struct){
+      A: (number){ |(*(int){ 0 }, (number){ >10 }) }
+      b: (number){ |(*(int){ 0 }, (number){ >10 }) }
+    }
+  }
   expr: (struct){
     t1: (struct){
       ok: (struct){
@@ -666,6 +682,16 @@ Result:
     }
   }
 }
+-- out/evalalpha/stats --
+Leaks:  288
+Freed:  16
+Reused: 16
+Allocs: 288
+Retain: 0
+
+Unifications: 258
+Conjuncts:    2303
+Disjuncts:    44
 -- out/evalalpha --
 Errors:
 definition.t0.err.d1.env.c: field not allowed:
@@ -812,6 +838,12 @@ Result:
       }
     }
   }
+  issue3194: (struct){
+    reduced: (#struct){
+      A: (number){ |(*(int){ 0 }, (number){ >10 }) }
+      b: (number){ |(*(int){ 0 }, (number){ >10 }) }
+    }
+  }
   expr: (struct){
     t1: (struct){
       ok: (struct){
@@ -1096,6 +1128,28 @@ Result:
     }
   }
 }
+-- diff/-out/evalalpha/stats<==>+out/eval/stats --
+diff old new
+--- old
++++ new
+@@ -1,9 +1,9 @@
+-Leaks:  4
+-Freed:  285
+-Reused: 273
+-Allocs: 16
+-Retain: 170
++Leaks:  288
++Freed:  16
++Reused: 16
++Allocs: 288
++Retain: 0
+
+-Unifications: 269
+-Conjuncts:    1619
+-Disjuncts:    436
++Unifications: 258
++Conjuncts:    2303
++Disjuncts:    44
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new
 --- old
@@ -1210,7 +1264,7 @@ diff old new
            }
            #A: (#struct){
              a: (int){ int }
-@@ -196,8 +179,7 @@
+@@ -202,8 +185,7 @@
        }
      }
    }
@@ -1220,7 +1274,7 @@ diff old new
      t0: (struct){
        ok: (struct){
          c: (struct){
-@@ -264,134 +246,130 @@
+@@ -270,134 +252,130 @@
          }
        }
      }
@@ -1479,7 +1533,7 @@ diff old new
              }
            }
          }
-@@ -401,23 +379,23 @@
+@@ -407,23 +385,23 @@
                d: (struct){
                  b: (int){ 2 }
                }
@@ -1695,6 +1749,23 @@ Reordering / positions.
     }
   }
 }
+--- equality.cue
+{
+  issue3194: {
+    reduced: {
+      A: (*0|>10)
+      A: (*0|>10)
+      {
+        out: close({
+          b: 〈2;A〉
+        })
+        out: {
+          b: 〈2;A〉
+        }
+      }.out
+    }
+  }
+}
 --- expr.cue
 {
   expr: {

internal/core/adt/disjunct2.go

@@ -706,7 +706,7 @@ func isEqualNodeValue(x, y *nodeContext) bool {
 	if x.hasTop != y.hasTop {
 		return false
 	}
-	if !isEqualBaseValue(x.ctx, x.scalar, y.scalar) {
+	if !isEqualValue(x.ctx, x.scalar, y.scalar) {
 		return false
 	}
 
@@ -718,10 +718,10 @@ func isEqualNodeValue(x, y *nodeContext) bool {
 		return false
 	}
 
-	if !isEqualBaseValue(x.ctx, x.lowerBound, y.lowerBound) {
+	if !isEqualValue(x.ctx, x.lowerBound, y.lowerBound) {
 		return false
 	}
-	if !isEqualBaseValue(x.ctx, x.upperBound, y.upperBound) {
+	if !isEqualValue(x.ctx, x.upperBound, y.upperBound) {
 		return false
 	}
 
@@ -749,15 +749,20 @@ func isEqualNodeValue(x, y *nodeContext) bool {
 	return true
 }
 
-func isEqualBaseValue(ctx *OpContext, x, y BaseValue) bool {
+type ComparableValue interface {
+	comparable
+	Value
+}
+
+func isEqualValue[P ComparableValue](ctx *OpContext, x, y P) bool {
+	var zero P
+
 	if x == y {
 		return true
 	}
-	xv, _ := x.(Value)
-	yv, _ := y.(Value)
-	if xv == nil || yv == nil {
+	if x == zero || y == zero {
 		return false
 	}
 
-	return Equal(ctx, xv, yv, CheckStructural)
+	return Equal(ctx, x, y, CheckStructural)
 }

internal/core/export/testdata/selfcontained/import.txtar

@@ -144,13 +144,13 @@ diff old new
 -	y: x
 -}
 +v: V
-
+ 
  // Do not simplify because of multiple usages of enclosing struct.
  x: B.c
 @@ -24,6 +21,12 @@
  run:     exec.Run
  _hidden: int
-
+ 
 +//cue:path: "mod.test/a/pkg".v.v
 +let V = {
 +	x: 3