[clang] Warning for unsafe invocation of span::data (PR #75650)

[Rashmi Mudduluru via cfe-commits]

================
@@ -721,6 +721,33 @@ class UnsafeBufferUsageAttrGadget : public WarningGadget {
   DeclUseList getClaimedVarUseSites() const override { return {}; }
 };
 
+// Warning gadget for unsafe invocation of span::data method.
+// Triggers when the pointer returned by the invocation is immediately
+// cast to a larger type.
+
+class DataInvocationGadget : public WarningGadget {
+  constexpr static const char *const OpTag = "data_invocation_expr";
+  const ExplicitCastExpr *Op;
+
+  public:
+  DataInvocationGadget(const MatchFinder::MatchResult &Result)
+      : WarningGadget(Kind::DataInvocation),
+        Op(Result.Nodes.getNodeAs<ExplicitCastExpr>(OpTag)) {}
+
+  static bool classof(const Gadget *G) {
+    return G->getKind() == Kind::DataInvocation;
+  }
+ 
+  static Matcher matcher() {
+    return stmt(
+        explicitCastExpr(has(cxxMemberCallExpr(callee(
+               cxxMethodDecl(hasName("data")))))).bind(OpTag));
----------------
t-rasmud wrote:

Will this also match on user defined functions called "data"? I think something like `cxxMethodDecl(ofClass(hasName("span")))` might be needed to match `span.data()` alone (but I might be wrong). In any case, maybe have a test case with a user defined function called "data" which'll show the matcher matches only on `span.data()`.

https://github.com/llvm/llvm-project/pull/75650