internal/core/compile: fix aliases to dynamic fields

For all orderings that is.

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I34156d7f22b3056737694de20132719a07166d1b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/542797
Unity-Result: CUEcueckoo <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Paul Jolly <[email protected]>

cue/testdata/compile/alias.txtar

@@ -0,0 +1,45 @@
+-- in.cue --
+dynamic: t1: {
+	X=(a): 1
+	x: X
+	a: "name"
+}
+
+dynamic: t2: {
+	x: X
+	X=(a): 1
+	a: "name"
+}
+-- out/compile --
+--- in.cue
+{
+  dynamic: {
+    t1: {
+      〈0;a〉: 1
+      x: 〈0;(〈0;a〉)〉
+      a: "name"
+    }
+  }
+  dynamic: {
+    t2: {
+      x: 〈0;(〈0;a〉)〉
+      〈0;a〉: 1
+      a: "name"
+    }
+  }
+}
+-- out/eval --
+(struct){
+  dynamic: (struct){
+    t1: (struct){
+      x: (int){ 1 }
+      a: (string){ "name" }
+      name: (int){ 1 }
+    }
+    t2: (struct){
+      x: (int){ 1 }
+      a: (string){ "name" }
+      name: (int){ 1 }
+    }
+  }
+}

internal/core/compile/compile.go

@@ -438,6 +438,9 @@ func (c *compiler) resolve(n *ast.Ident) adt.Expr {
 	// Local expressions
 	case *ast.LetClause:
 		entry := c.lookupAlias(k, n)
+		if entry.expr == nil {
+			panic("unreachable")
+		}
 
 		// let x = y
 		return &adt.LetReference{
@@ -544,14 +547,6 @@ func (c *compiler) decl(d ast.Decl) adt.Decl {
 			if lab, ok = a.Expr.(ast.Label); !ok {
 				return c.errf(a, "alias expression is not a valid label")
 			}
-
-			switch lab.(type) {
-			case *ast.Ident, *ast.BasicLit, *ast.ListLit:
-				// Even though we won't need the alias, we still register it
-				// for duplicate and failed reference detection.
-			default:
-				c.updateAlias(a.Ident, c.expr(a.Expr))
-			}
 		}
 
 		v := x.Value
@@ -678,6 +673,23 @@ func (c *compiler) addLetDecl(d ast.Decl) {
 		expr := c.labeledExpr(nil, (*letScope)(x), x.Expr)
 		c.updateAlias(x.Ident, expr)
 
+	case *ast.Field:
+		lab := x.Label
+		if a, ok := lab.(*ast.Alias); ok {
+			if lab, ok = a.Expr.(ast.Label); !ok {
+				// error reported elsewhere
+				return
+			}
+
+			switch lab.(type) {
+			case *ast.Ident, *ast.BasicLit, *ast.ListLit:
+				// Even though we won't need the alias, we still register it
+				// for duplicate and failed reference detection.
+			default:
+				c.updateAlias(a.Ident, c.expr(a.Expr))
+			}
+		}
+
 	case *ast.Alias:
 		c.errf(x, "old-style alias no longer supported: use let clause; use cue fix to update.")
 	}