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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Nicolas van Kempen (nicovank)

<details>
<summary>Changes</summary>

`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
&gt; cat tmp.cpp
int a = 13;
int b = ((int) a) - a;
int c = a - ((int) a);

&gt; clang-query tmp.cpp
clang-query&gt; set traversal IgnoreUnlessSpelledInSource
clang-query&gt; 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.

&gt; ./build/bin/clang-query tmp.cpp
clang-query&gt; set traversal IgnoreUnlessSpelledInSource
clang-query&gt; 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.

---
Full diff: https://github.com/llvm/llvm-project/pull/104148.diff


1 Files Affected:

- (modified) clang/include/clang/ASTMatchers/ASTMatchers.h (+1-1) 


``````````diff
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);
 }
 

``````````

</details>


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