internal/core/adt: report error for integer fields

These are currently not supported.

Fixes #1516

Signed-off-by: Marcel van Lohuizen <mpvl@golang.org>

Change-Id: I41529d4068a580e9bbc593f8743cb0e5987c8912
Signed-off-by: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/533472
Reviewed-by: Paul Jolly <paul@myitcv.io>

Author: mpvl

cue/testdata/comprehensions/errors.txtar

@@ -22,10 +22,19 @@ userError: {
     if a != "" {
     }
 }
+
+intField: {
+	for i, _ in [1, 2] {
+		(i): {
+		}
+	  }
+}
 -- out/eval --
 Errors:
 circularFor.#list: invalid operand tail != null (found bool, want list or struct):
     ./in.cue:12:18
+intField: integer fields not supported:
+    ./in.cue:27:4
 
 Result:
 (_|_){
@@ -51,6 +60,14 @@ Result:
     //     ./in.cue:20:8
     a: (string){ string }
   }
+  intField: (_|_){
+    // [eval] intField: integer fields not supported:
+    //     ./in.cue:27:4
+    0: (struct){
+    }
+    1: (struct){
+    }
+  }
 }
 -- out/compile --
 --- in.cue
@@ -71,4 +88,12 @@ Result:
     a: (string|*_|_(explicit error (_|_ literal) in source))
     if (〈0;a〉 != "") {}
   }
+  intField: {
+    for i, _ in [
+      1,
+      2,
+    ] {
+      〈1;i〉: {}
+    }
+  }
 }

cue/testdata/eval/fields.txtar

@@ -5,6 +5,9 @@ bulkToSelf: {
         foo: bar: "3" // error
     }
 }
+intField: {
+	(2): string
+}
 -- out/compile --
 --- in.cue
 {
@@ -18,12 +21,17 @@ bulkToSelf: {
       }
     }
   }
+  intField: {
+    2: string
+  }
 }
 -- out/eval --
 Errors:
 bulkToSelf.a.foo.bar: conflicting values "3" and int (mismatched types string and int):
     ./in.cue:3:24
     ./in.cue:4:19
+intField: integer fields not supported:
+    ./in.cue:8:3
 
 Result:
 (_|_){
@@ -42,4 +50,9 @@ Result:
       }
     }
   }
+  intField: (_|_){
+    // [eval] intField: integer fields not supported:
+    //     ./in.cue:8:3
+    2: (string){ string }
+  }
 }

internal/core/adt/eval.go

@@ -1958,6 +1958,9 @@ func (n *nodeContext) injectDynamic() (progress bool) {
 			continue
 		}
 		f = ctx.Label(d.field.Key, v)
+		if f.IsInt() {
+			n.addErr(ctx.NewPosf(pos(d.field.Key), "integer fields not supported"))
+		}
 		n.insertField(f, MakeConjunct(d.env, d.field, d.id))
 	}