Move SHOULD/MUST statements to each bullet point

Co-authored-by: Andreas Heigl <[email protected]>

Author: Crell

src/Pure.php

@@ -28,17 +28,17 @@
  * 2. The function has no side effects (no mutation of non-local variables,
  *    mutable reference arguments or input/output streams).
  *
- * In PHP, that means a pure function MUST NOT:
+ * In PHP, that means a pure function:
  *
- * 1. Use or modify any global variable.
- * 2. Perform any IO operations, even read-only ones.
- * 3. Modify any property of an object provided to it as an argument,
- *    even transitively.
- * 4. Read from an object property on the same object unless that property
- *    is `readonly`.
- * 5. Accept a parameter by reference.
- * 6. Call any function that is not also marked "pure." (It may invoke a
- *    callable passed to it as an explicit argument.)
+ * 1. MUST NOT use or modify any global variable.
+ * 2. MIST NOT perform any IO operations, even read-only ones.
+ * 3. MUST NOT modify any property of an object provided to it as an 
+ *    argument, even transitively.
+ * 4. MUST NOT read from an object property on the same object unless 
+ *    that property is `readonly`.
+ * 5. MUST NOT accept a parameter by reference.
+ * 6. MUST NOT call any function that is not also marked "pure." (It 
+ *    may invoke a callable passed to it as an explicit argument.)
  *
  * ## When should the attribute be applied
  *
@@ -48,20 +48,23 @@
  *  If this attribute is placed on a method in an interface, it means that all
  *  implementations of that method MUST themselves be marked pure.
  *
- * Static analysis tools SHOULD
- * - Verify that the function indeed meets the rules above, and treat it as
- *    an error if not.
+ * Static analysis tools
+ * - SHOULD verify that the function indeed meets the rules above, 
+ *   and treat it as an error if not.
  *
- * Static analysis tools MUST
- * - Treat PHP standard library functions that conform to these rules as pure.
- *    As an example, `strtolower()` is pure.  `sort()` is not.
- * - Flag as an error any function that is marked pure but is demonstrably not.
- * - Treat any method implementing an interface method marked pure as pure.
+ * Static analysis tools
+ * - MUST treat PHP standard library functions that conform to these 
+ *   rules as pure. As an example, `strtolower()` is pure.  `sort()`
+ *   is not.
+ * - MUST flag as an error any function that is marked pure but is 
+ *   demonstrably not.
+ * - MUST treat any method implementing an interface method marked
+ *   pure as pure.
  *
- * Optimization tools and pre-compilation tools MAY:
- * - Implement optimizations based on the knowledge that a function is pure.
- *   For example, they may safely cache its results indefinitely, or inline its
- *   code into another routine.
+ * Optimization tools and pre-compilation tools:
+ * - MAY implement optimizations based on the knowledge that a function 
+ *   is pure. For example, they may safely cache its results indefinitely, 
+ *   or inline its code into another routine.
  *
  */
 #[\Attribute(\Attribute::TARGET_FUNCTION | \Attribute::TARGET_METHOD)]