[clang-tools-extra] [clang-tidy] Enhance modernize-use-starts-ends-with to handle substr patterns (PR #116033)

[Helmut Januschka via cfe-commits]

================
@@ -171,10 +182,64 @@ void UseStartsEndsWithCheck::registerMatchers(MatchFinder *Finder) {
                              hasRHS(lengthExprForStringNode("needle")))))
           .bind("expr"),
       this);
+
+  Finder->addMatcher(
+      cxxOperatorCallExpr(
+          hasAnyOperatorName("==", "!="),
+          anyOf(
+              hasOperands(
+                  cxxMemberCallExpr(
+                      argumentCountIs(2), hasArgument(0, ZeroLiteral),
+                      hasArgument(1, lengthExprForStringNode("needle")),
+                      callee(
+                          cxxMethodDecl(hasName("substr"),
+                                        ofClass(OnClassWithStartsWithFunction))
+                              .bind("find_fun")))
+                      .bind("find_expr"),
+                  expr().bind("needle")),
+              hasOperands(expr().bind("needle"),
+                          cxxMemberCallExpr(
+                              argumentCountIs(2), hasArgument(0, ZeroLiteral),
+                              hasArgument(1, lengthExprForStringNode("needle")),
+                              callee(cxxMethodDecl(
+                                         hasName("substr"),
+                                         ofClass(OnClassWithStartsWithFunction))
+                                         .bind("find_fun")))
+                              .bind("find_expr"))))
+          .bind("expr"),
+      this);
----------------
hjanuschka wrote:

🙈 i am super impressed, and the more i learn about AST the more i know i know nothing!
do you have any good resources to ramp up the knowledge in this area? (trying to sourcegraph search, copy&paste, trial-and-error so far)

https://github.com/llvm/llvm-project/pull/116033