From 91ca3269a1b544db1303b496101fd9d6fe953277 Mon Sep 17 00:00:00 2001
From: Artem Dergachev <artem.dergachev@gmail.com>
Date: Mon, 3 May 2021 14:32:37 -0700
Subject: [PATCH] [clang-tidy] Aliasing: Add support for aggregates with
 references.

When a variable is used in an initializer of an aggregate
for its reference-type field this counts as aliasing.

Differential Revision: https://reviews.llvm.org/D101791
---
 clang-tools-extra/clang-tidy/utils/Aliasing.cpp    |  7 ++++++
 .../clang-tidy/checkers/bugprone-infinite-loop.cpp | 26 ++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/clang-tools-extra/clang-tidy/utils/Aliasing.cpp b/clang-tools-extra/clang-tidy/utils/Aliasing.cpp
index 12a8ca8..69aea11 100644
--- a/clang-tools-extra/clang-tidy/utils/Aliasing.cpp
+++ b/clang-tools-extra/clang-tidy/utils/Aliasing.cpp
@@ -50,6 +50,13 @@ static bool isPtrOrReferenceForVar(const Stmt *S, const VarDecl *Var) {
   } else if (const auto *LE = dyn_cast<LambdaExpr>(S)) {
     // Treat lambda capture by reference as a form of taking a reference.
     return capturesByRef(LE->getLambdaClass(), Var);
+  } else if (const auto *ILE = dyn_cast<InitListExpr>(S)) {
+    return llvm::any_of(ILE->inits(), [Var](const Expr *ChildE) {
+      // If the child expression is a reference to Var, this means that it's
+      // used as an initializer of a reference-typed field. Otherwise
+      // it would have been surrounded with an implicit lvalue-to-rvalue cast.
+      return isAccessForVar(ChildE, Var);
+    });
   }
 
   return false;
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone-infinite-loop.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone-infinite-loop.cpp
index 5b47713..2765b18 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone-infinite-loop.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone-infinite-loop.cpp
@@ -566,3 +566,29 @@ int foo(void) {
   }
   return 0;
 }
+
+struct AggregateWithReference {
+  int &y;
+};
+
+void test_structured_bindings_good() {
+  int x = 0;
+  AggregateWithReference ref { x };
+  auto &[y] = ref;
+  for (; x < 10; ++y) {
+    // No warning. The loop is finite because 'y' is a reference to 'x'.
+  }
+}
+
+struct AggregateWithValue {
+  int y;
+};
+
+void test_structured_bindings_bad() {
+  int x = 0;
+  AggregateWithValue val { x };
+  auto &[y] = val;
+  for (; x < 10; ++y) {
+      // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: this loop is infinite; none of its condition variables (x) are updated in the loop body [bugprone-infinite-loop]
+  }
+}
-- 
2.7.4