[clang] [clang][ASTMatcher] Fix execution order of hasOperands submatchers (PR #104148)

[Nicolas van Kempen via cfe-commits]

https://github.com/nicovank created https://github.com/llvm/llvm-project/pull/104148

`hasOperands` does not always execute matchers in the order they are written. This can cause issue in code using bindings when one operand matcher is relying on a binding set by the other. With this change, the first matcher present in the code is always executed first and any binding it sets are available to the second matcher.

Simple example with current version (1 match) and new version (2 matches):
```bash
> cat tmp.cpp
int a = 13;
int b = ((int) a) - a;
int c = a - ((int) a);

> clang-query tmp.cpp
clang-query> set traversal IgnoreUnlessSpelledInSource
clang-query> m binaryOperator(hasOperands(cStyleCastExpr(has(declRefExpr(hasDeclaration(valueDecl().bind("d"))))), declRefExpr(hasDeclaration(valueDecl(equalsBoundNode("d"))))))

Match #1:

tmp.cpp:1:1: note: "d" binds here
int a = 13;
^~~~~~~~~~
tmp.cpp:2:9: note: "root" binds here
int b = ((int)a) - a;
        ^~~~~~~~~~~~
1 match.

> ./build/bin/clang-query tmp.cpp
clang-query> set traversal IgnoreUnlessSpelledInSource
clang-query> m binaryOperator(hasOperands(cStyleCastExpr(has(declRefExpr(hasDeclaration(valueDecl().bind("d"))))), declRefExpr(hasDeclaration(valueDecl(equalsBoundNode("d"))))))

Match #1:

tmp.cpp:1:1: note: "d" binds here
    1 | int a = 13;
      | ^~~~~~~~~~
tmp.cpp:2:9: note: "root" binds here
    2 | int b = ((int)a) - a;
      |         ^~~~~~~~~~~~

Match #2:

tmp.cpp:1:1: note: "d" binds here
    1 | int a = 13;
      | ^~~~~~~~~~
tmp.cpp:3:9: note: "root" binds here
    3 | int c = a - ((int)a);
      |         ^~~~~~~~~~~~
2 matches.
```

If this should be documented or regression tested anywhere please let me know where.

>From 6391d7d4a4ebe6132ef465ddab00c3b88d3c1719 Mon Sep 17 00:00:00 2001
From: Nicolas van Kempen <nvankemp at gmail.com>
Date: Wed, 14 Aug 2024 14:34:43 -0400
Subject: [PATCH] [clang][ASTMatcher] Fix execution order of hasOperands
 submatchers

`hasOperands` does not always execute matchers in the order they are written.
This can cause issue in code using bindings when one operand matcher is relying
on a binding set by the other. With this change, the first matcher present in
the code is always executed first and any binding it sets are available to the
second matcher.

Simple example with current version (1 match) and new version (2 matches):
```bash
> cat tmp.cpp
int a = 13;
int b = ((int) a) - a;
int c = a - ((int) a);

> clang-query tmp.cpp
clang-query> set traversal IgnoreUnlessSpelledInSource
clang-query> m binaryOperator(hasOperands(cStyleCastExpr(has(declRefExpr(hasDeclaration(valueDecl().bind("d"))))), declRefExpr(hasDeclaration(valueDecl(equalsBoundNode("d"))))))

Match #1:

tmp.cpp:1:1: note: "d" binds here
int a = 13;
^~~~~~~~~~
tmp.cpp:2:9: note: "root" binds here
int b = ((int)a) - a;
        ^~~~~~~~~~~~
1 match.

> ./build/bin/clang-query tmp.cpp
clang-query> set traversal IgnoreUnlessSpelledInSource
clang-query> m binaryOperator(hasOperands(cStyleCastExpr(has(declRefExpr(hasDeclaration(valueDecl().bind("d"))))), declRefExpr(hasDeclaration(valueDecl(equalsBoundNode("d"))))))

Match #1:

tmp.cpp:1:1: note: "d" binds here
    1 | int a = 13;
      | ^~~~~~~~~~
tmp.cpp:2:9: note: "root" binds here
    2 | int b = ((int)a) - a;
      |         ^~~~~~~~~~~~

Match #2:

tmp.cpp:1:1: note: "d" binds here
    1 | int a = 13;
      | ^~~~~~~~~~
tmp.cpp:3:9: note: "root" binds here
    3 | int c = a - ((int)a);
      |         ^~~~~~~~~~~~
2 matches.
```
---
 clang/include/clang/ASTMatchers/ASTMatchers.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
index ca44c3ee085654..f1c72efc238784 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -6027,7 +6027,7 @@ AST_POLYMORPHIC_MATCHER_P2(
     internal::Matcher<Expr>, Matcher1, internal::Matcher<Expr>, Matcher2) {
   return internal::VariadicDynCastAllOfMatcher<Stmt, NodeType>()(
              anyOf(allOf(hasLHS(Matcher1), hasRHS(Matcher2)),
-                   allOf(hasLHS(Matcher2), hasRHS(Matcher1))))
+                   allOf(hasRHS(Matcher1), hasLHS(Matcher2))))
       .matches(Node, Finder, Builder);
 }