1 files changed, 64 insertions, 0 deletions
diff --git a/build/clang-plugin/MustUseChecker.cpp b/build/clang-plugin/MustUseChecker.cpp
new file mode 100644
index 0000000000..92acb7ff5b
--- /dev/null
+++ b/build/clang-plugin/MustUseChecker.cpp
@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MustUseChecker.h"
+#include "CustomMatchers.h"
+#include "CustomTypeAnnotation.h"
+
+CustomTypeAnnotation MustUse =
+    CustomTypeAnnotation(moz_must_use_type, "must-use");
+
+void MustUseChecker::registerMatchers(MatchFinder *AstMatcher) {
+  AstMatcher->addMatcher(switchCase().bind("switchcase"), this);
+  AstMatcher->addMatcher(compoundStmt().bind("compound"), this);
+  AstMatcher->addMatcher(ifStmt().bind("if"), this);
+  AstMatcher->addMatcher(whileStmt().bind("while"), this);
+  AstMatcher->addMatcher(doStmt().bind("do"), this);
+  AstMatcher->addMatcher(forStmt().bind("for"), this);
+  AstMatcher->addMatcher(binaryOperator(binaryCommaOperator()).bind("bin"),
+                         this);
+}
+
+void MustUseChecker::check(const MatchFinder::MatchResult &Result) {
+  if (auto SC = Result.Nodes.getNodeAs<SwitchCase>("switchcase")) {
+    handleUnusedExprResult(SC->getSubStmt());
+  }
+  if (auto C = Result.Nodes.getNodeAs<CompoundStmt>("compound")) {
+    for (const auto &S : C->body()) {
+      handleUnusedExprResult(S);
+    }
+  }
+  if (auto IF = Result.Nodes.getNodeAs<IfStmt>("if")) {
+    handleUnusedExprResult(IF->getThen());
+    handleUnusedExprResult(IF->getElse());
+  }
+  if (auto W = Result.Nodes.getNodeAs<WhileStmt>("while")) {
+    handleUnusedExprResult(W->getBody());
+  }
+  if (auto D = Result.Nodes.getNodeAs<DoStmt>("do")) {
+    handleUnusedExprResult(D->getBody());
+  }
+  if (auto F = Result.Nodes.getNodeAs<ForStmt>("for")) {
+    handleUnusedExprResult(F->getBody());
+    handleUnusedExprResult(F->getInit());
+    handleUnusedExprResult(F->getInc());
+  }
+  if (auto C = Result.Nodes.getNodeAs<BinaryOperator>("bin")) {
+    handleUnusedExprResult(C->getLHS());
+  }
+}
+
+void MustUseChecker::handleUnusedExprResult(const Stmt *Statement) {
+  const Expr *E = dyn_cast_or_null<Expr>(Statement);
+  if (E) {
+    E = E->IgnoreImplicit(); // Ignore ExprWithCleanup etc. implicit wrappers
+    QualType T = E->getType();
+    if (MustUse.hasEffectiveAnnotation(T) && !isIgnoredExprForMustUse(E)) {
+      diag(E->getBeginLoc(), "Unused value of must-use type %0",
+           DiagnosticIDs::Error)
+          << T;
+      MustUse.dumpAnnotationReason(*this, T, E->getBeginLoc());
+    }
+  }
+}