-- x.cue --
// variants of fib

inline: small: {
	f: {
		n: int
		out: (f & {"n": n - 1}).out
	}
}

inline: medium: {
	f2:  (f & {n: 2}).out
	fRec: {nn: int, out: (f & {n: nn}).out}
	f: {
		n: int
		out: (fRec & {nn: n - 1}).out
	}
}

inline: patterns: {
	f: n: (f & {n: {}}).n
	f: n: {}
	[string]: {n: {}}
	f: [string]: {}
	f: {}
}

inline: acrossFields: fail1: {
	f: {
		in:  number
		out: in + 1
	}
	k00: 0
	k10: (f & {in: k00}).out
	k20: (f & {in: k10}).out
	k30: (f & {in: k20}).out

	// invalid recursion is here.
	k10: (f & {in: k30}).out
}

// Issue #2163
inline: acrossFields: ok1: {
	f: {
		in:  number
		out: in
	}
	k00: 0
	k10: (f & {in: k00}).out
	k20: (f & {in: k10}).out
	k30: (f & {in: k20}).out

	// TODO: what is correct behavior here.
	// This is borderline okay.
	k10: (f & {in: k30}).out
}
-- out/compile --
--- x.cue
{
  inline: {
    small: {
      f: {
        n: int
        out: (〈1;f〉 & {
          n: (〈1;n〉 - 1)
        }).out
      }
    }
  }
  inline: {
    medium: {
      f2: (〈0;f〉 & {
        n: 2
      }).out
      fRec: {
        nn: int
        out: (〈1;f〉 & {
          n: 〈1;nn〉
        }).out
      }
      f: {
        n: int
        out: (〈1;fRec〉 & {
          nn: (〈1;n〉 - 1)
        }).out
      }
    }
  }
  inline: {
    patterns: {
      f: {
        n: (〈1;f〉 & {
          n: {}
        }).n
      }
      f: {
        n: {}
      }
      [string]: {
        n: {}
      }
      f: {
        [string]: {}
      }
      f: {}
    }
  }
  inline: {
    acrossFields: {
      fail1: {
        f: {
          in: number
          out: (〈0;in〉 + 1)
        }
        k00: 0
        k10: (〈0;f〉 & {
          in: 〈1;k00〉
        }).out
        k20: (〈0;f〉 & {
          in: 〈1;k10〉
        }).out
        k30: (〈0;f〉 & {
          in: 〈1;k20〉
        }).out
        k10: (〈0;f〉 & {
          in: 〈1;k30〉
        }).out
      }
    }
  }
  inline: {
    acrossFields: {
      ok1: {
        f: {
          in: number
          out: 〈0;in〉
        }
        k00: 0
        k10: (〈0;f〉 & {
          in: 〈1;k00〉
        }).out
        k20: (〈0;f〉 & {
          in: 〈1;k10〉
        }).out
        k30: (〈0;f〉 & {
          in: 〈1;k20〉
        }).out
        k10: (〈0;f〉 & {
          in: 〈1;k30〉
        }).out
      }
    }
  }
}
-- out/eval/stats --
Leaks:  247
Freed:  141
Reused: 136
Allocs: 252
Retain: 834

Unifications: 388
Conjuncts:    1307
Disjuncts:    707
-- out/eval --
Errors:
structural cycle:
    ./x.cue:6:9
structural cycle:
    ./x.cue:15:9
structural cycle:
    ./x.cue:20:9
in: structural cycle:
    ./x.cue:30:8

Result:
(_|_){
  // [structural cycle]
  inline: (_|_){
    // [structural cycle]
    small: (_|_){
      // [structural cycle]
      f: (_|_){
        // [structural cycle]
        n: (int){ int }
        out: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:6:9
        }
      }
    }
    medium: (_|_){
      // [structural cycle]
      f2: (_|_){
        // [structural cycle] structural cycle:
        //     ./x.cue:15:9
      }
      fRec: (_|_){
        // [structural cycle]
        nn: (int){ int }
        out: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:15:9
        }
      }
      f: (_|_){
        // [structural cycle]
        n: (int){ int }
        out: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:15:9
        }
      }
    }
    patterns: (_|_){
      // [structural cycle]
      f: (_|_){
        // [structural cycle]
        n: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:20:9
        }
      }
    }
    acrossFields: (_|_){
      // [structural cycle]
      fail1: (_|_){
        // [structural cycle]
        f: (struct){
          in: (number){ number }
          out: (_|_){
            // [incomplete] inline.acrossFields.fail1.f.out: non-concrete value number in operand to +:
            //     ./x.cue:30:8
            //     ./x.cue:29:8
          }
        }
        k00: (int){ 0 }
        k10: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:30:8
        }
        k20: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:30:8
        }
        k30: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:30:8
        }
      }
      ok1: (struct){
        f: (struct){
          in: (number){ number }
          out: (number){ number }
        }
        k00: (int){ 0 }
        k10: (int){ 0 }
        k20: (int){ 0 }
        k30: (int){ 0 }
      }
    }
  }
}
-- out/evalalpha --
Errors:
structural cycle:
    ./x.cue:6:9
structural cycle:
    ./x.cue:12:24
structural cycle:
    ./x.cue:15:9
structural cycle:
    ./x.cue:20:9
in: structural cycle:
    ./x.cue:34:17
in: structural cycle:
    ./x.cue:35:17
in: structural cycle:
    ./x.cue:38:17
in: structural cycle:
    ./x.cue:49:17
in: structural cycle:
    ./x.cue:50:17
in: structural cycle:
    ./x.cue:54:17

Result:
(_|_){
  // [structural cycle]
  inline: (_|_){
    // [structural cycle]
    small: (_|_){
      // [structural cycle]
      f: (_|_){
        // [structural cycle]
        n: (int){ int }
        out: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:6:9
        }
      }
    }
    medium: (_|_){
      // [structural cycle]
      f2: (_|_){
        // [structural cycle] structural cycle:
        //     ./x.cue:15:9
      }
      fRec: (_|_){
        // [structural cycle]
        nn: (int){ int }
        out: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:12:24
        }
      }
      f: (_|_){
        // [structural cycle]
        n: (int){ int }
        out: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:15:9
        }
      }
    }
    patterns: (_|_){
      // [structural cycle]
      f: (_|_){
        // [structural cycle]
        n: (_|_){
          // [structural cycle] structural cycle:
          //     ./x.cue:20:9
        }
      }
    }
    acrossFields: (_|_){
      // [structural cycle]
      fail1: (_|_){
        // [structural cycle]
        f: (struct){
          in: (number){ number }
          out: (_|_){
            // [incomplete] inline.acrossFields.fail1.f.out: non-concrete value number in operand to +:
            //     ./x.cue:30:8
            //     ./x.cue:29:8
          }
        }
        k00: (int){ 0 }
        k10: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:38:17
        }
        k20: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:34:17
        }
        k30: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:35:17
        }
      }
      ok1: (_|_){
        // [structural cycle]
        f: (struct){
          in: (number){ number }
          out: (number){ number }
        }
        k00: (int){ 0 }
        k10: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:54:17
        }
        k20: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:49:17
        }
        k30: (_|_){
          // [structural cycle] in: structural cycle:
          //     ./x.cue:50:17
        }
      }
    }
  }
}
-- diff/-out/evalalpha<==>+out/eval --
diff old new
--- old
+++ new
@@ -2,11 +2,23 @@
 structural cycle:
     ./x.cue:6:9
 structural cycle:
+    ./x.cue:12:24
+structural cycle:
     ./x.cue:15:9
 structural cycle:
     ./x.cue:20:9
 in: structural cycle:
-    ./x.cue:30:8
+    ./x.cue:34:17
+in: structural cycle:
+    ./x.cue:35:17
+in: structural cycle:
+    ./x.cue:38:17
+in: structural cycle:
+    ./x.cue:49:17
+in: structural cycle:
+    ./x.cue:50:17
+in: structural cycle:
+    ./x.cue:54:17
 
 Result:
 (_|_){
@@ -35,7 +47,7 @@
         nn: (int){ int }
         out: (_|_){
           // [structural cycle] structural cycle:
-          //     ./x.cue:15:9
+          //     ./x.cue:12:24
         }
       }
       f: (_|_){
@@ -72,26 +84,36 @@
         k00: (int){ 0 }
         k10: (_|_){
           // [structural cycle] in: structural cycle:
-          //     ./x.cue:30:8
-        }
-        k20: (_|_){
-          // [structural cycle] in: structural cycle:
-          //     ./x.cue:30:8
-        }
-        k30: (_|_){
-          // [structural cycle] in: structural cycle:
-          //     ./x.cue:30:8
-        }
-      }
-      ok1: (struct){
+          //     ./x.cue:38:17
+        }
+        k20: (_|_){
+          // [structural cycle] in: structural cycle:
+          //     ./x.cue:34:17
+        }
+        k30: (_|_){
+          // [structural cycle] in: structural cycle:
+          //     ./x.cue:35:17
+        }
+      }
+      ok1: (_|_){
+        // [structural cycle]
         f: (struct){
           in: (number){ number }
           out: (number){ number }
         }
         k00: (int){ 0 }
-        k10: (int){ 0 }
-        k20: (int){ 0 }
-        k30: (int){ 0 }
+        k10: (_|_){
+          // [structural cycle] in: structural cycle:
+          //     ./x.cue:54:17
+        }
+        k20: (_|_){
+          // [structural cycle] in: structural cycle:
+          //     ./x.cue:49:17
+        }
+        k30: (_|_){
+          // [structural cycle] in: structural cycle:
+          //     ./x.cue:50:17
+        }
       }
     }
   }
-- diff/todo/p2 --
One test now fails. Given TODO, this may be okay.
This does break Issue #2163.