copy values on return

onflow · Aug 28, 2020 · 25897c7 · 25897c7
1 parent 82669f5
commit 25897c7
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Showing 2 changed files with 30 additions and 1 deletion.
diff --git a/runtime/interpreter/interpreter.go b/runtime/interpreter/interpreter.go
@@ -1089,7 +1089,8 @@ func (interpreter *Interpreter) VisitReturnStatement(statement *ast.ReturnStatem
 			valueType := interpreter.Checker.Elaboration.ReturnStatementValueTypes[statement]
 			returnType := interpreter.Checker.Elaboration.ReturnStatementReturnTypes[statement]
 
-			value = interpreter.convertAndBox(value, valueType, returnType)
+			// NOTE: copy on return
+			value = interpreter.copyAndConvert(value, valueType, returnType)
 
 			return functionReturn{value}
 		})

diff --git a/runtime/tests/interpreter/interpreter_test.go b/runtime/tests/interpreter/interpreter_test.go
@@ -8175,3 +8175,31 @@ func TestInterpretInternalAssignment(t *testing.T) {
 		value,
 	)
 }
+
+func TestInterpretCopyOnReturn(t *testing.T) {
+
+	t.Parallel()
+
+	inter := parseCheckAndInterpret(t,
+		`
+          let xs: {String: String} = {}
+
+          fun returnXS(): {String: String} {
+              return xs
+          }
+
+          fun test(): {String: String} {
+              returnXS().insert(key: "foo", "bar")
+              return xs
+          }
+        `,
+	)
+
+	value, err := inter.Invoke("test")
+	require.NoError(t, err)
+
+	assert.Equal(t,
+		interpreter.NewDictionaryValueUnownedNonCopying(),
+		value,
+	)
+}