internal: fix crash affecting eval

Change-Id: I92d854690c926dee045e866d4caf1c6922af2e36
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/5640
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/cmd/cue/cmd/testdata/script/eval_import.txt b/cmd/cue/cmd/testdata/script/eval_import.txt
new file mode 100644
index 0000000..56f7006
--- /dev/null
+++ b/cmd/cue/cmd/testdata/script/eval_import.txt
@@ -0,0 +1,15 @@
+cue eval ./in.cue
+cmp stdout expect-stdout
+-- expect-stdout --
+import "list"
+
+def: {
+    types :: list.MinItems(1)
+}
+-- in.cue --
+import (
+	"list"
+)
+
+def: types :: list.MinItems(1)
+
diff --git a/internal/internal.go b/internal/internal.go
index 63ec888..d71a2ec 100644
--- a/internal/internal.go
+++ b/internal/internal.go
@@ -188,6 +188,8 @@
 	case ast.Expr:
 		ast.SetRelPos(x, token.NoSpace)
 		return &ast.File{Decls: []ast.Decl{&ast.EmbedDecl{Expr: x}}}
+	case *ast.File:
+		return x
 	default:
 		panic(fmt.Sprintf("Unsupported node type %T", x))
 	}