Rollup merge of #104147 - WaffleLapkin:don't-compare-ptr-addresses-in-parser-, r=compiler-errors

Remove an address comparison from the parser

Originally this check was added in #68985, as suggested by 940f657#r376850175. I don't think that this address check is a robust way of making parser more robust.

This code is also extensively tested by [`ui/parser/issues/issue-35813-postfix-after-cast.rs`](https://github.com/rust-lang/rust/blob/57d3c58ed6e0faf89a62411f96c000ffc9fd3937/src/test/ui/parser/issues/issue-35813-postfix-after-cast.rs).

_Replaces #103700_

r? `@compiler-errors`

Author: GuillaumeGomez

compiler/rustc_parse/src/parser/expr.rs

@@ -833,16 +833,11 @@ impl<'a> Parser<'a> {
                 ("cast", None)
             };
 
-        // Save the memory location of expr before parsing any following postfix operators.
-        // This will be compared with the memory location of the output expression.
-        // If they different we can assume we parsed another expression because the existing expression is not reallocated.
-        let addr_before = &*cast_expr as *const _ as usize;
         let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
-        let changed = addr_before != &*with_postfix as *const _ as usize;
 
         // Check if an illegal postfix operator has been added after the cast.
-        // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
-        if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {
+        // If the resulting expression is not a cast, it is an illegal postfix operator.
+        if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
             let msg = format!(
                 "{cast_kind} cannot be followed by {}",
                 match with_postfix.kind {