internal/core/adt: ensure pattern is evaluated

The old evaluator handled patterns differently. Ensure
patterns are evaluated before used.

This also fixes a case where a nil pointer was referenced
when computing an error position.

Fixes #3412

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: I13e89de6a1fe25ad4161c61a0e450360981f2f0e
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1200588
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Matthew Sackman <matthew@cue.works>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

cue/testdata/builtins/all.txtar

@@ -16,16 +16,24 @@ okIncompleteChild: {
 	b: {}
 	x: and([{a: b.c}, {b: 1}])
 }
+-- issue3412.cue --
+andInPattern: {
+	out: {
+		[and(#constraints)]: _
+		someKey: {}
+	}
+	#constraints: [=~"^.*$"]
+}
 -- out/eval/stats --
 Leaks:  2
-Freed:  12
-Reused: 8
-Allocs: 6
-Retain: 2
+Freed:  18
+Reused: 12
+Allocs: 8
+Retain: 3
 
-Unifications: 14
-Conjuncts:    17
-Disjuncts:    14
+Unifications: 20
+Conjuncts:    27
+Disjuncts:    21
 -- out/evalalpha --
 Errors:
 fatalArg.x: invalid operands "eee" and 'eee' to '+' (type string and bytes):
@@ -65,6 +73,15 @@ Result:
       b: (int){ 1 }
     }
   }
+  andInPattern: (struct){
+    out: (struct){
+      someKey: (struct){
+      }
+    }
+    #constraints: (#list){
+      0: (string){ =~"^.*$" }
+    }
+  }
 }
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new
@@ -137,6 +154,15 @@ Result:
       b: (int){ 1 }
     }
   }
+  andInPattern: (struct){
+    out: (struct){
+      someKey: (struct){
+      }
+    }
+    #constraints: (#list){
+      0: (string){ =~"^.*$" }
+    }
+  }
 }
 -- out/compile --
 --- in.cue
@@ -164,3 +190,15 @@ Result:
     ])
   }
 }
+--- issue3412.cue
+{
+  andInPattern: {
+    out: {
+      [and(〈1;#constraints〉)]: _
+      someKey: {}
+    }
+    #constraints: [
+      =~"^.*$",
+    ]
+  }
+}

internal/core/adt/composite.go

@@ -328,8 +328,12 @@ func (v *Vertex) updateArcType(t ArcType) {
 	if (s != nil || v.isFinal()) && s.ctx.isDevVersion() {
 		c := s.ctx
 		if s.scheduler.frozen.meets(arcTypeKnown) {
+			p := token.NoPos
+			if src := c.Source(); src != nil {
+				p = src.Pos()
+			}
 			parent := v.Parent
-			parent.reportFieldCycleError(c, c.Source().Pos(), v.Label)
+			parent.reportFieldCycleError(c, p, v.Label)
 			return
 		}
 	}

internal/core/adt/constraints.go

@@ -134,6 +134,9 @@ func matchPattern(ctx *OpContext, pattern Value, f Feature) bool {
 // This is an optimization an intended to be faster than regular CUE evaluation
 // for the majority of cases where pattern constraints are used.
 func matchPatternValue(ctx *OpContext, pattern Value, f Feature, label Value) (result bool) {
+	if v, ok := pattern.(*Vertex); ok {
+		v.unify(ctx, scalarKnown, finalize)
+	}
 	pattern = Unwrap(pattern)
 	label = Unwrap(label)