pkg/encoding/json: add tests for issue 3932

Issue #3932

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I4897cd71b4959a760ebb02eb5447259af6ba59e9
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1215527
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mpvl

pkg/encoding/json/testdata/gen.txtar

@@ -20,6 +20,11 @@ validate: enforceRequired: {
 	schema: {x!: int}
 }
 
+issue3932: {
+	f: json.Validate({name!: string})
+	f: json.Marshal({name: "foo"})
+}
+
 valid: [string]: {
 	string // input
 	#result: json.Valid(string)
@@ -96,9 +101,9 @@ validate.t2.result: error in call to encoding/json.Validate: invalid value 10 (o
     ./in.cue:9:27
     json.Validate:1:6
 unmarshal.trailingInvalid.#result: error in call to encoding/json.Unmarshal: json: invalid JSON:
-    ./in.cue:42:11
+    ./in.cue:47:11
 unmarshal.trailingValid.#result: error in call to encoding/json.Unmarshal: json: invalid JSON:
-    ./in.cue:42:11
+    ./in.cue:47:11
 
 Result:
 import "encoding/json"
@@ -146,6 +151,13 @@ validate: {
 		result: json.Validate(str, schema)
 	}
 }
+issue3932: {
+	f: json.Validate({
+		name!: string
+	}) & json.Marshal({
+		name: "foo"
+	})
+}
 valid: {
 	t1: {
 		"1"