[clang-tidy] bugprone-string-integer-assignment: Reduce false positives.

Summary: Detect a few expressions as likely character expressions, see PR27723.

Reviewers: xazax.hun, alexfh

Subscribers: rnkovacs, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58609

llvm-svn: 355089

1 files changed, 7 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/bugprone-string-integer-assignment.cpp b/clang-tools-extra/test/clang-tidy/bugprone-string-integer-assignment.cpp
index 2b73f89bf12..dbf3a5c5e60 100644
--- a/clang-tools-extra/test/clang-tidy/bugprone-string-integer-assignment.cpp
+++ b/clang-tools-extra/test/clang-tidy/bugprone-string-integer-assignment.cpp
@@ -59,4 +59,11 @@ int main() {
   s += toupper(x);
   s += tolower(x);
   s += std::tolower(x);
+
+  // Likely character expressions.
+  s += x & 0xff;
+  s += 0xff & x;
+
+  s += 'a' + (x % 26);
+  s += (x % 10) + 'b';
 }