Fixed that scoped variables would overwrite parent scope.

Fixes #952

changelog/952.md

@@ -0,0 +1 @@
+- Fixed that scoped variables would overwrite parent scope [#952](https://github.com/smarty-php/smarty/issues/952)

src/Data.php

@@ -127,13 +127,15 @@ public function assign($tpl_var, $value = null, $nocache = false, $scope = null)
 			case self::SCOPE_LOCAL:
 			default:
 				if (isset($this->tpl_vars[$tpl_var])) {
-					$this->tpl_vars[$tpl_var]->setValue($value);
+					$newVariable = clone $this->tpl_vars[$tpl_var];
+					$newVariable->setValue($value);
 					if ($nocache) {
-						$this->tpl_vars[$tpl_var]->setNocache(true);
+						$newVariable->setNocache(true);
 					}
 				} else {
-					$this->tpl_vars[$tpl_var] = new Variable($value, $nocache);
+					$newVariable = new Variable($value, $nocache);
 				}
+				$this->tpl_vars[$tpl_var] = $newVariable;
 		}
 
         return $this;

tests/UnitTests/TemplateSource/X_Scopes/ScopeTest.php

@@ -325,4 +325,13 @@ public function testFunctionScope()
         $this->smarty->assign('scope', 'none');
         $r = $this->smarty->fetch('test_function_scope.tpl');
     }
+
+	public function testFunctionScopeIsLocaLByDefault()
+	{
+		$this->assertEquals(
+			'a',
+			$this->smarty->fetch('string:{function name=test}{$var="b"}{/function}{$var="a"}{test}{$var}')
+		);
+	}
+
 }