Better disambiguation between subscript-expression and compound-statement

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
php
Domain
compilers

Research direction

Reproduce the PHP snippet and inspect the parser rules or entry points handling subscript-expression, if statements, and compound statements. Confirm the corrected parse keeps the missing-parenthesis error associated with the if statement and preserves c() as a method of class A.

Written by the indexing model from the issue text.

Description

bug error-handling up-for-grabs

This error tolerance case needs some special handling.

class A {
    function b() {
        if ($expression {
            $a = 3;
            $b = "hello";
        }
        echo "hi";
    }
    
    public function c() {
    }
}

In this case, the if statement is missing a close paren. However, rather than getting parsed as an if-statement missing a close paren, it gets parsed as a subscript-expression (which is defined as follows, according to the PHP language spec.

subscript-expression:
  dereferencable-expression   [   expressionopt   ]
  dereferencable-expression   {   expression   }   <b>[Deprecated form]</b>

This results in the first close brace getting treated as a close brace for the method, rather than the if statement. Then the next close brace gets eaten by the Class node (which terminates the class), so c() ends up being a function, rather than a method.

Dominant language
PHP
Stars
894
Forks
85
Avg merge
2d 13h
Merged PRs (30d)
3

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