LibJS: Parse while statements

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/038051d2056
Pull-request: https://github.com/SerenityOS/serenity/pull/1906
Reviewed-by: https://github.com/alimpfard

Libraries/LibJS/Parser.cpp

@@ -249,6 +249,8 @@ NonnullRefPtr<Statement> Parser::parse_statement()
         return parse_switch_statement();
     case TokenType::Do:
         return parse_do_while_statement();
+    case TokenType::While:
+        return parse_while_statement();
     default:
         if (match_expression()) {
             auto expr = parse_expression(0);
@@ -847,6 +849,20 @@ NonnullRefPtr<DoWhileStatement> Parser::parse_do_while_statement()
     return create_ast_node<DoWhileStatement>(move(test), move(body));
 }
 
+NonnullRefPtr<WhileStatement> Parser::parse_while_statement()
+{
+    consume(TokenType::While);
+    consume(TokenType::ParenOpen);
+
+    auto test = parse_expression(0);
+
+    consume(TokenType::ParenClose);
+
+    auto body = parse_statement();
+
+    return create_ast_node<WhileStatement>(move(test), move(body));
+}
+
 NonnullRefPtr<SwitchStatement> Parser::parse_switch_statement()
 {
     consume(TokenType::Switch);

Libraries/LibJS/Parser.h

@@ -60,6 +60,7 @@ public:
     NonnullRefPtr<BreakStatement> parse_break_statement();
     NonnullRefPtr<ContinueStatement> parse_continue_statement();
     NonnullRefPtr<DoWhileStatement> parse_do_while_statement();
+    NonnullRefPtr<WhileStatement> parse_while_statement();
     NonnullRefPtr<ConditionalExpression> parse_conditional_expression(NonnullRefPtr<Expression> test);
 
     NonnullRefPtr<Expression> parse_expression(int min_precedence, Associativity associate = Associativity::Right);

Libraries/LibJS/Tests/while-basic.js

@@ -0,0 +1,21 @@
+load("test-common.js");
+
+try {
+    var number = 0;
+    while (number < 9) {
+        number++;
+    }
+    assert(number === 9);
+
+    number = 0;
+    while(number < 3) number++;
+    assert(number === 3);
+
+    while (false) {
+        assertNotReached();
+    }
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}