================
@@ -36,6 +36,111 @@ void extractNodesByIdTo(ArrayRef<BoundNodes> Matches,
StringRef ID,
Nodes.insert(Match.getNodeAs<Node>(ID));
}
+// If `D` has a const-qualified overload with otherwise identical
+// ref-qualifiers, returns that overload.
+const CXXMethodDecl *findConstOverload(const CXXMethodDecl &D) {
+ assert(!D.isConst());
+
+ DeclContext::lookup_result lookup_result =
+ D.getParent()->lookup(D.getNameInfo().getName());
+ if (lookup_result.isSingleResult()) {
+ // No overload.
+ return nullptr;
+ }
+ for (const Decl *overload : lookup_result) {
+ const CXXMethodDecl *candidate = dyn_cast<CXXMethodDecl>(overload);
+ if (candidate && !candidate->isDeleted() && candidate->isConst() &&
+ candidate->getRefQualifier() == D.getRefQualifier()) {
+ return candidate;
+ }
+ }
+ return nullptr;
+}
+
+// Returns true if both types refer to the same to the same type,
+// ignoring the const-qualifier.
+bool isSameTypeIgnoringConst(QualType A, QualType B) {
+ A = A.getCanonicalType();
+ B = B.getCanonicalType();
+ A.addConst();
+ B.addConst();
+ return A == B;
+}
+
+// Returns true if both types are pointers or reference to the same type,
+// ignoring the const-qualifier.
+bool pointsToSameTypeIgnoringConst(QualType A, QualType B) {
+ assert(A->isPointerType() || A->isReferenceType());
+ assert(B->isPointerType() || B->isReferenceType());
+ return isSameTypeIgnoringConst(A->getPointeeType(), B->getPointeeType());
+}
+
+// Return true if non-const member function `M` likely does not mutate `*this`.
+//
+// Note that if the member call selects a method/operator `f` that
+// is not const-qualified, then we also consider that the object is
+// not mutated if:
+// - (A) there is a const-qualified overload `cf` of `f` that has
+// the
+// same ref-qualifiers;
+// - (B) * `f` returns a value, or
+// * if `f` returns a `T&`, `cf` returns a `const T&` (up to
+// possible aliases such as `reference` and
+// `const_reference`), or
+// * if `f` returns a `T*`, `cf` returns a `const T*` (up to
+// possible aliases).
+// - (C) the result of the call is not mutated.
+//
+// The assumption that `cf` has the same semantics as `f`.
+// For example:
+// - In `std::vector<T> v; const T t = v[...];`, we consider that
+// expression `v[...]` does not mutate `v` as
+// `T& std::vector<T>::operator[]` has a const overload
+// `const T& std::vector<T>::operator[] const`, and the
+// result expression of type `T&` is only used as a `const T&`;
+// - In `std::map<K, V> m; V v = m.at(...);`, we consider
+// `m.at(...)` to be an immutable access for the same reason.
+// However:
+// - In `std::map<K, V> m; const V v = m[...];`, We consider that
+// `m[...]` mutates `m` as `V& std::map<K, V>::operator[]` does
+// not have a const overload.
+// - In `std::vector<T> v; T& t = v[...];`, we consider that
+// expression `v[...]` mutates `v` as the result is kept as a
+// mutable reference.
+//
+// This function checks (A) ad (B), but the caller should make sure that the
+// object is not mutated through the return value.
+bool isLikelyShallowConst(const CXXMethodDecl &M) {
+ assert(!M.isConst());
+ // The method can mutate our variable.
+
+ // (A)
+ const CXXMethodDecl *ConstOverload = findConstOverload(M);
+ if (ConstOverload == nullptr) {
+ return false;
+ }
+
+ // (B)
+ const QualType CallTy = M.getReturnType().getCanonicalType();
+ const QualType OverloadTy =
ConstOverload->getReturnType().getCanonicalType();
+ if (CallTy->isReferenceType()) {
+ if (!(OverloadTy->isReferenceType() &&
----------------
fberger wrote:
I would find: `(!isReferenceType() || !pointsToSameTypIgnoringConst(....))`
easier to parse here.
https://github.com/llvm/llvm-project/pull/94362
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