Add (and ignore for now) type assertions to QML

You can write "(something as Foo)" to give hints to any tools that you
expect something to be a Foo at this place. This is not a conversion and
ignored at runtime for now. Eventually the compiler will verify that the
type assertions are plausible and error out if they aren't.

Change-Id: I21c8705bb387f7ab2cbc153293dbf477663afe87
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

4 files changed, 60 insertions, 1 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index c43ea64e2e..fff6a2fe4c 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -1497,7 +1497,9 @@ bool Codegen::visit(BinaryExpression *ast)
 
         break;
     }
-
+    case QSOperator::As:
+        setExprResult(left);
+        break;
     } // switch
 
     return false;
diff --git a/src/qml/parser/qqmljs.g b/src/qml/parser/qqmljs.g
index f7b528ce13..ea105e7e22 100644
--- a/src/qml/parser/qqmljs.g
+++ b/src/qml/parser/qqmljs.g
@@ -2513,6 +2513,20 @@ RelationalExpression_In: RelationalExpression_In T_IN ShiftExpression;
     } break;
 ./
 
+TypeAssertExpression_In: RelationalExpression_In T_AS Type;
+/.  case $rule_number: Q_FALLTHROUGH(); ./
+TypeAssertExpression: RelationalExpression T_AS Type;
+/.
+    case $rule_number: {
+        AST::BinaryExpression *node = new (pool) AST::BinaryExpression(sym(1).Expression, QSOperator::As, sym(3).Expression);
+        node->operatorToken = loc(2);
+        sym(1).Node = node;
+    } break;
+./
+
+RelationalExpression_In: TypeAssertExpression_In;
+RelationalExpression: TypeAssertExpression;
+
 EqualityExpression_In: RelationalExpression_In;
 EqualityExpression: RelationalExpression;
 
diff --git a/src/qml/parser/qqmljsast_p.h b/src/qml/parser/qqmljsast_p.h
index fcf9933e67..bc0a467f40 100644
--- a/src/qml/parser/qqmljsast_p.h
+++ b/src/qml/parser/qqmljsast_p.h
@@ -104,6 +104,7 @@ enum Op {
     URShift,
     InplaceURightShift,
     InplaceXor,
+    As,
     Invalid
 };
 
diff --git a/tests/auto/qml/qqmlparser/tst_qqmlparser.cpp b/tests/auto/qml/qqmlparser/tst_qqmlparser.cpp
index 4ba6a709df..76b56bd303 100644
--- a/tests/auto/qml/qqmlparser/tst_qqmlparser.cpp
+++ b/tests/auto/qml/qqmlparser/tst_qqmlparser.cpp
@@ -63,6 +63,8 @@ private slots:
     void disallowedTypeAnnotations_data();
     void disallowedTypeAnnotations();
     void semicolonPartOfExpressionStatement();
+    void typeAssertion_data();
+    void typeAssertion();
 
 private:
     QStringList excludedDirs;
@@ -479,6 +481,46 @@ void tst_qqmlparser::semicolonPartOfExpressionStatement()
     QVERIFY(observer.endsWithSemicolon);
 }
 
+void tst_qqmlparser::typeAssertion_data()
+{
+    QTest::addColumn<QString>("expression");
+    QTest::addRow("as A")
+            << QString::fromLatin1("A { onStuff: (b as A).happen() }");
+    QTest::addRow("as double paren")
+            << QString::fromLatin1("A { onStuff: console.log((12 as double)); }");
+    QTest::addRow("as double noparen")
+            << QString::fromLatin1("A { onStuff: console.log(12 as double); }");
+    QTest::addRow("property as double")
+            << QString::fromLatin1("A { prop: (12 as double); }");
+    QTest::addRow("property noparen as double")
+            << QString::fromLatin1("A { prop: 12 as double; }");
+
+    // rabbits cannot be discerned from types on a syntactical level.
+    // We could detect this on a semantical level, once we implement type assertions there.
+
+    QTest::addRow("as rabbit")
+            << QString::fromLatin1("A { onStuff: (b as rabbit).happen() }");
+    QTest::addRow("as rabbit paren")
+            << QString::fromLatin1("A { onStuff: console.log((12 as rabbit)); }");
+    QTest::addRow("as rabbit noparen")
+            << QString::fromLatin1("A { onStuff: console.log(12 as rabbit); }");
+    QTest::addRow("property as rabbit")
+            << QString::fromLatin1("A { prop: (12 as rabbit); }");
+    QTest::addRow("property noparen as rabbit")
+            << QString::fromLatin1("A { prop: 12 as rabbit; }");
+}
+
+void tst_qqmlparser::typeAssertion()
+{
+    QFETCH(QString, expression);
+
+    QQmlJS::Engine engine;
+    QQmlJS::Lexer lexer(&engine);
+    lexer.setCode(expression, 1);
+    QQmlJS::Parser parser(&engine);
+    QVERIFY(parser.parse());
+}
+
 QTEST_MAIN(tst_qqmlparser)
 
 #include "tst_qqmlparser.moc"