5 files changed, 80 insertions, 3 deletions
diff --git a/src/qmlcompiler/qqmljslinter.cpp b/src/qmlcompiler/qqmljslinter.cpp
index 595a512992..13f5a0a362 100644
--- a/src/qmlcompiler/qqmljslinter.cpp
+++ b/src/qmlcompiler/qqmljslinter.cpp
@@ -608,7 +608,7 @@ QQmlJSLinter::LintResult QQmlJSLinter::lintFile(const QString &filename,
     QQmlJS::LinterVisitor v{ target, &m_importer, m_logger.get(),
                              QQmlJSImportVisitor::implicitImportDirectory(
                                      m_logger->filePath(), m_importer.resourceFileMapper()),
-                             qmldirFiles };
+                             qmldirFiles, &engine };
 
     if (m_enablePlugins) {
         for (const Plugin &plugin : m_plugins) {
diff --git a/src/qmlcompiler/qqmljslintervisitor.cpp b/src/qmlcompiler/qqmljslintervisitor.cpp
index e08567a26f..2705fc945e 100644
--- a/src/qmlcompiler/qqmljslintervisitor.cpp
+++ b/src/qmlcompiler/qqmljslintervisitor.cpp
@@ -17,6 +17,15 @@ namespace QQmlJS {
    are purely syntactic checks, or style-checks warnings that don't make sense during compilation.
  */
 
+LinterVisitor::LinterVisitor(
+        const QQmlJSScope::Ptr &target, QQmlJSImporter *importer, QQmlJSLogger *logger,
+        const QString &implicitImportDirectory, const QStringList &qmldirFiles,
+        QQmlJS::Engine *engine)
+    : QQmlJSImportVisitor(target, importer, logger, implicitImportDirectory, qmldirFiles)
+    , m_engine(engine)
+{
+}
+
 bool LinterVisitor::visit(StringLiteral *sl)
 {
     QQmlJSImportVisitor::visit(sl);
@@ -267,6 +276,62 @@ bool LinterVisitor::visit(QQmlJS::AST::UiEnumDeclaration *uied)
     return true;
 }
 
+void LinterVisitor::checkCaseFallthrough(StatementList *statements, SourceLocation errorLoc,
+                                         SourceLocation nextLoc)
+{
+    if (!statements || !nextLoc.isValid())
+        return;
+
+    quint32 afterLastStatement = 0;
+    for (StatementList *it = statements; it; it = it->next) {
+        if (!it->next) {
+            Node::Kind kind = (Node::Kind) it->statement->kind;
+            if (kind == Node::Kind_BreakStatement || kind == Node::Kind_ReturnStatement
+                || kind == Node::Kind_ThrowStatement) {
+                return;
+            }
+            afterLastStatement = it->statement->lastSourceLocation().end();
+        }
+    }
+
+    const auto &comments = m_engine->comments();
+    auto it = std::find_if(comments.cbegin(), comments.cend(),
+                           [&](auto c) { return afterLastStatement < c.offset; });
+    auto end = std::find_if(it, comments.cend(),
+                            [&](auto c) { return c.offset >= nextLoc.offset; });
+
+    for (; it != end; ++it) {
+        const QString &commentText = m_engine->code().mid(it->offset, it->length);
+        if (commentText.contains("fall through"_L1)
+            || commentText.contains("fall-through"_L1)
+            || commentText.contains("fallthrough"_L1)) {
+            return;
+        }
+    }
+
+    m_logger->log("Unterminated non-empty case block"_L1, qmlUnterminatedCase, errorLoc);
+}
+
+bool LinterVisitor::visit(QQmlJS::AST::CaseBlock *block)
+{
+    QQmlJSImportVisitor::visit(block);
+
+    std::vector<std::pair<SourceLocation, StatementList *>> clauses;
+    for (CaseClauses *it = block->clauses; it; it = it->next)
+        clauses.push_back({ it->clause->caseToken, it->clause->statements });
+    if (block->defaultClause)
+        clauses.push_back({ block->defaultClause->defaultToken, block->defaultClause->statements });
+    for (CaseClauses *it = block->moreClauses; it; it = it->next)
+        clauses.push_back({ it->clause->caseToken, it->clause->statements });
+
+    // check all but the last clause for fallthrough
+    for (size_t i = 0; i < clauses.size() - 1; ++i) {
+        const SourceLocation nextToken = clauses[i + 1].first;
+        checkCaseFallthrough(clauses[i].second, clauses[i].first, nextToken);
+    }
+    return true;
+}
+
 } // namespace QQmlJS
 
 QT_END_NAMESPACE
diff --git a/src/qmlcompiler/qqmljslintervisitor_p.h b/src/qmlcompiler/qqmljslintervisitor_p.h
index c485428af4..48e9372887 100644
--- a/src/qmlcompiler/qqmljslintervisitor_p.h
+++ b/src/qmlcompiler/qqmljslintervisitor_p.h
@@ -16,6 +16,8 @@
 
 #include <private/qqmljsimportvisitor_p.h>
 
+#include <private/qqmljsengine_p.h>
+
 QT_BEGIN_NAMESPACE
 
 namespace QQmlJS {
@@ -29,7 +31,9 @@ namespace QQmlJS {
 class LinterVisitor final : public QQmlJSImportVisitor
 {
 public:
-    using QQmlJSImportVisitor::QQmlJSImportVisitor;
+    LinterVisitor(const QQmlJSScope::Ptr &target, QQmlJSImporter *importer, QQmlJSLogger *logger,
+                  const QString &implicitImportDirectory,
+                  const QStringList &qmldirFiles = QStringList(), QQmlJS::Engine *engine = nullptr);
 
 protected:
     using QQmlJSImportVisitor::endVisit;
@@ -46,6 +50,7 @@ protected:
     bool visit(QQmlJS::AST::BinaryExpression *) override;
     bool visit(QQmlJS::AST::UiImport *import) override;
     bool visit(QQmlJS::AST::UiEnumDeclaration *uied) override;
+    bool visit(QQmlJS::AST::CaseBlock *) override;
 
 private:
     struct SeenImport
@@ -75,11 +80,15 @@ private:
             return qHashMulti(seed, i.filename, i.uri, i.version, i.id);
         }
     };
+    QQmlJS::Engine *m_engine = nullptr;
     QSet<SeenImport> m_seenImports;
     std::vector<QQmlJS::AST::Node *> m_ancestryIncludingCurrentNode;
 
     void handleDuplicateEnums(QQmlJS::AST::UiEnumMemberList *members, QStringView key,
                               const QQmlJS::SourceLocation &location);
+    void warnCaseNoFlowControl(QQmlJS::SourceLocation caseToken) const;
+    void checkCaseFallthrough(QQmlJS::AST::StatementList *statements, SourceLocation errorLoc,
+                              SourceLocation nextLoc);
 };
 
 } // namespace QQmlJS
diff --git a/src/qmlcompiler/qqmljslogger.cpp b/src/qmlcompiler/qqmljslogger.cpp
index 77d9bfc1e9..c01ae212f0 100644
--- a/src/qmlcompiler/qqmljslogger.cpp
+++ b/src/qmlcompiler/qqmljslogger.cpp
@@ -88,6 +88,9 @@ using namespace Qt::StringLiterals;
       "Warn about non-list properties", QtWarningMsg, false, false)                                \
     X(qmlNonRootEnums, "non-root-enum", "NonRootEnum",                                             \
       "Warn about enums defined outside the root component", QtWarningMsg, false, false)           \
+    X(qmlUnterminatedCase, "unterminated-case", "UnterminatedCase", "Warn about non-empty case "   \
+      "blocks that are not terminated by control flow or by a fallthrough comment",                \
+      QtWarningMsg, false, false)                                                                  \
     X(qmlPlugin, "plugin", "LintPluginWarnings", "Warn if a qmllint plugin finds an issue",        \
       QtWarningMsg, true, false)                                                                   \
     X(qmlPrefixedImportType, "prefixed-import-type", "PrefixedImportType",                         \
@@ -139,7 +142,6 @@ using namespace Qt::StringLiterals;
       "positives when checking for unqualified access",                                            \
       QtWarningMsg, false, false)
 
-
 #define X(category, name, setting, description, level, ignored, isDefault) \
     const QQmlSA::LoggerWarningId category{ name };
 QMLLINT_DEFAULT_CATEGORIES
diff --git a/src/qmlcompiler/qqmljsloggingutils.h b/src/qmlcompiler/qqmljsloggingutils.h
index fe3a76c742..f87f76d414 100644
--- a/src/qmlcompiler/qqmljsloggingutils.h
+++ b/src/qmlcompiler/qqmljsloggingutils.h
@@ -88,6 +88,7 @@ extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnqualified;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnreachableCode;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnresolvedAlias;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnresolvedType;
+extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnterminatedCase;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnusedImports;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUseProperFunction;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlVarUsedBeforeDeclaration;