Add basic type annotation support for QML functions to the grammar

Inspired by TypeScript syntax, allow optional type annotations in the
style of ": <name of type>" in for the parameters of functions and their
return type.

These annotations are not used at the moment, so by default we produce
an error message when encountering them in the AST.

In addition their usage is limited to functions declared in the QML
scope. All other uses attempt to produce readable syntax errors. So for
example this is okay:

    Item {
        function blah(param: string) string { ... }
    }

And this is not okay:

    // some file.js
    function blah(param: string) : string { ... }

Change-Id: I12d20b4e2ce92e01108132975a06cfd13ba4a254
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

3 files changed, 15 insertions, 0 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 453963c1dd..6248348d8e 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -610,6 +610,8 @@ void Codegen::initializeAndDestructureBindingElement(AST::PatternElement *e, con
     if (hasError())
         return;
 
+    accept(e->typeAnnotation);
+
     if (e->initializer) {
         if (!baseRef.isValid()) {
             // assignment
@@ -885,6 +887,12 @@ bool Codegen::visit(ExportDeclaration *ast)
     return false;
 }
 
+bool Codegen::visit(TypeAnnotation *ast)
+{
+    throwSyntaxError(ast->firstSourceLocation(), QLatin1String("Type annotations are not supported (yet)."));
+    return false;
+}
+
 bool Codegen::visit(StatementList *)
 {
     Q_UNREACHABLE();
diff --git a/src/qml/compiler/qv4codegen_p.h b/src/qml/compiler/qv4codegen_p.h
index 51b821aafe..ef710b5648 100644
--- a/src/qml/compiler/qv4codegen_p.h
+++ b/src/qml/compiler/qv4codegen_p.h
@@ -593,6 +593,8 @@ protected:
 
     bool visit(AST::ExportDeclaration *ast) override;
 
+    bool visit(AST::TypeAnnotation *ast) override;
+
     // expressions
     bool visit(AST::Expression *ast) override;
     bool visit(AST::ArrayPattern *ast) override;
diff --git a/src/qml/compiler/qv4compilerscanfunctions.cpp b/src/qml/compiler/qv4compilerscanfunctions.cpp
index 416a0edee0..11da6605c3 100644
--- a/src/qml/compiler/qv4compilerscanfunctions.cpp
+++ b/src/qml/compiler/qv4compilerscanfunctions.cpp
@@ -679,6 +679,11 @@ bool ScanFunctions::enterFunction(Node *ast, const QString &name, FormalParamete
             _context->isArrowFunction = true;
         else if (expr->isGenerator)
             _context->isGenerator = true;
+
+        if (expr->typeAnnotation) {
+            _cg->throwSyntaxError(ast->firstSourceLocation(), QLatin1String("Type annotations are not supported (yet)."));
+            return false;
+        }
     }