Improve error handling + test the RuleType/TokenType casting better

Author: ciaranmcnulty

php/src/Parser/TokenRuleTypesCastTrait.php

@@ -8,26 +8,26 @@
 
 trait TokenRuleTypesCastTrait
 {
-    public static function cast(TokenType $tokenType): RuleType
+    public static function cast(TokenType $tokenType): self
     {
         $tokenName = $tokenType->name;
 
         if ($tokenName != TokenType::None->name) {
             $tokenName = '_' . $tokenName;
         }
 
-        $newValueString = RuleType::class . '::' . $tokenName;
+        // PHP does not currently support MyClass::$myConstant as a syntax
+        // so the `constant()` function has to be used instead, by constructing
+        // a string that refers to the enum case name
+        $newValueString = self::class . '::' . $tokenName;
 
         if (!defined($newValueString)) {
-            throw new LogicException('Could not create RuleType from TokenType::' . $tokenName);
+            throw new LogicException('Could not create RuleType from TokenType::' . $tokenType->name);
         }
 
+        /** @var self $ruleType */
         $ruleType = constant($newValueString);
 
-        if (!$ruleType instanceof RuleType) {
-            throw new LogicException('Could not create RuleType from TokenType::' . $tokenName);
-        }
-
         return $ruleType;
     }
 }

php/tests/unit/Parser/RuleTypeTest.php

@@ -15,6 +15,14 @@ public function testItCanCastFromTokens(TokenType $tokenType): void
         self::assertInstanceOf(RuleType::class, RuleType::cast($tokenType));
     }
 
+    public function testItCanFailIfEnumDoesNotHaveMatchingValue(): void
+    {
+        $this->expectException(\LogicException::class);
+        $this->expectExceptionMessage('Could not create RuleType from TokenType::Comment');
+
+        TooShortEnum::cast(TokenType::Comment);
+    }
+
     /**
      * @return Generator<string,array{0:TokenType}>
      */
@@ -25,3 +33,13 @@ public function tokenCaseProvider(): Generator
         }
     }
 }
+
+/**
+ * An enum fixture that deliberately doesn't have cases matching TokenType
+ */
+enum TooShortEnum
+{
+    use TokenRuleTypesCastTrait;
+
+    case Foo;
+}