LibPDF: In ColorSpace creation code, use resolve_to() more

For valid PDFs, this makes no difference.

For invalid PDFs, we now assert during the cast in resolve_to() instead
of returning a PDFError. However, most PDFs are valid, and even for
invalid PDFs, we'd previously keep the old color space around when
getting the PDF error and then usually assert later when the old
color space got passed a color with an unexpected number of components
(since the components were for the new color space).

Doesn't affect any of the > 2000 PDFs I use for testing locally,
is less code, and should make for less surprising asserts when it
does happen.

Userland/Libraries/LibPDF/ColorSpace.cpp

@@ -314,11 +314,7 @@ PDFErrorOr<NonnullRefPtr<CalGrayColorSpace>> CalGrayColorSpace::create(Document*
     if (parameters.size() != 1)
         return Error { Error::Type::MalformedPDF, "Gray color space expects one parameter" };
 
-    auto param = TRY(document->resolve(parameters[0]));
+    auto dict = TRY(document->resolve_to<DictObject>(parameters[0]));
-    if (!param.has<NonnullRefPtr<Object>>() || !param.get<NonnullRefPtr<Object>>()->is<DictObject>())
-        return Error { Error::Type::MalformedPDF, "Gray color space expects a dict parameter" };
-
-    auto dict = param.get<NonnullRefPtr<Object>>()->cast<DictObject>();
     if (!dict->contains(CommonNames::WhitePoint))
         return Error { Error::Type::MalformedPDF, "Gray color space expects a Whitepoint key" };
 
@@ -384,11 +380,7 @@ PDFErrorOr<NonnullRefPtr<CalRGBColorSpace>> CalRGBColorSpace::create(Document* d
     if (parameters.size() != 1)
         return Error { Error::Type::MalformedPDF, "RGB color space expects one parameter" };
 
-    auto param = TRY(document->resolve(parameters[0]));
+    auto dict = TRY(document->resolve_to<DictObject>(parameters[0]));
-    if (!param.has<NonnullRefPtr<Object>>() || !param.get<NonnullRefPtr<Object>>()->is<DictObject>())
-        return Error { Error::Type::MalformedPDF, "RGB color space expects a dict parameter" };
-
-    auto dict = param.get<NonnullRefPtr<Object>>()->cast<DictObject>();
     if (!dict->contains(CommonNames::WhitePoint))
         return Error { Error::Type::MalformedPDF, "RGB color space expects a Whitepoint key" };
 
@@ -478,11 +470,7 @@ PDFErrorOr<NonnullRefPtr<ColorSpace>> ICCBasedColorSpace::create(Document* docum
     if (parameters.is_empty())
         return Error { Error::Type::MalformedPDF, "ICCBased color space expected one parameter" };
 
-    auto param = TRY(document->resolve(parameters[0]));
+    auto stream = TRY(document->resolve_to<StreamObject>(parameters[0]));
-    if (!param.has<NonnullRefPtr<Object>>() || !param.get<NonnullRefPtr<Object>>()->is<StreamObject>())
-        return Error { Error::Type::MalformedPDF, "ICCBased color space expects a stream parameter" };
-
-    auto stream = param.get<NonnullRefPtr<Object>>()->cast<StreamObject>();
     auto dict = stream->dict();
 
     auto maybe_profile = Gfx::ICC::Profile::try_load_from_externally_owned_memory(stream->bytes());
@@ -554,11 +542,7 @@ PDFErrorOr<NonnullRefPtr<LabColorSpace>> LabColorSpace::create(Document* documen
     if (parameters.size() != 1)
         return Error { Error::Type::MalformedPDF, "Lab color space expects one parameter" };
 
-    auto param = TRY(document->resolve(parameters[0]));
+    auto dict = TRY(document->resolve_to<DictObject>(parameters[0]));
-    if (!param.has<NonnullRefPtr<Object>>() || !param.get<NonnullRefPtr<Object>>()->is<DictObject>())
-        return Error { Error::Type::MalformedPDF, "Lab color space expects a dict parameter" };
-
-    auto dict = param.get<NonnullRefPtr<Object>>()->cast<DictObject>();
     if (!dict->contains(CommonNames::WhitePoint))
         return Error { Error::Type::MalformedPDF, "Lab color space expects a Whitepoint key" };
 
@@ -644,10 +628,7 @@ PDFErrorOr<NonnullRefPtr<ColorSpace>> IndexedColorSpace::create(Document* docume
     //  in the color table are to be interpreted. It can be any device or CIE-based color space or (in PDF 1.3)
     //  a Separation or DeviceN space, but not a Pattern space or another Indexed space."
 
-    auto param0 = TRY(document->resolve(parameters[0]));
+    auto base_object = TRY(document->resolve_to<Object>(parameters[0]));
-    if (!param0.has<NonnullRefPtr<Object>>())
-        return Error { Error::Type::MalformedPDF, "Indexed color space expects object for first arg" };
-    auto base_object = param0.get<NonnullRefPtr<Object>>();
     auto base = TRY(ColorSpace::create(document, base_object));
 
     if (base->family() == ColorSpaceFamily::Pattern || base->family() == ColorSpaceFamily::Indexed)
@@ -655,10 +636,7 @@ PDFErrorOr<NonnullRefPtr<ColorSpace>> IndexedColorSpace::create(Document* docume
 
     // "The hival parameter is an integer that specifies the maximum valid index value. In other words,
     // the color table is to be indexed by integers in the range 0 to hival. hival can be no greater than 255"
-    auto param1 = TRY(document->resolve(parameters[1]));
+    auto hival = TRY(document->resolve_to<int>(parameters[1]));
-    if (!param1.has<int>())
-        return Error { Error::Type::MalformedPDF, "Indexed color space expects int for second arg" };
-    auto hival = param1.get<int>();
 
     // "The color table is defined by the lookup parameter, which can be either a stream or (in PDF 1.2) a byte string.
     //  It provides the mapping between index values and the corresponding colors in the base color space.
@@ -666,10 +644,7 @@ PDFErrorOr<NonnullRefPtr<ColorSpace>> IndexedColorSpace::create(Document* docume
     //  base color space. Each byte is an unsigned integer in the range 0 to 255 that is scaled to the range of
     //  the corresponding color component in the base color space; that is, 0 corresponds to the minimum value
     //  in the range for that component, and 255 corresponds to the maximum."
-    auto param2 = TRY(document->resolve(parameters[2]));
+    auto lookup_object = TRY(document->resolve_to<Object>(parameters[2]));
-    if (!param2.has<NonnullRefPtr<Object>>())
-        return Error { Error::Type::MalformedPDF, "Indexed color space expects object for third arg" };
-    auto lookup_object = param2.get<NonnullRefPtr<Object>>();
 
     Vector<u8> lookup;
     if (lookup_object->is<StreamObject>()) {
@@ -724,21 +699,13 @@ PDFErrorOr<NonnullRefPtr<SeparationColorSpace>> SeparationColorSpace::create(Doc
 
     // "The name parameter is a name object specifying the name of the colorant that this Separation color space
     //  is intended to represent (or one of the special names All or None; see below)"
-    auto param0 = TRY(document->resolve(parameters[0]));
+    auto name_object = TRY(document->resolve_to<NameObject>(parameters[0]));
-    if (!param0.has<NonnullRefPtr<Object>>())
-        return Error { Error::Type::MalformedPDF, "Separation color space expects object for first arg" };
-    auto name_object = param0.get<NonnullRefPtr<Object>>();
-    if (!name_object->is<NameObject>())
-        return Error { Error::Type::MalformedPDF, "Separation color space expects name object for first arg" };
     auto name = name_object->cast<NameObject>()->name();
 
     // "The alternateSpace parameter must be an array or name object that identifies the alternate color space,
     //  which can be any device or CIE-based color space but not another special color space
     //  (Pattern, Indexed, Separation, or DeviceN)."
-    auto param1 = TRY(document->resolve(parameters[1]));
+    auto alternate_space_object = TRY(document->resolve_to<Object>(parameters[1]));
-    if (!param1.has<NonnullRefPtr<Object>>())
-        return Error { Error::Type::MalformedPDF, "Separation color space expects object for second arg" };
-    auto alternate_space_object = param1.get<NonnullRefPtr<Object>>();
     auto alternate_space = TRY(ColorSpace::create(document, alternate_space_object));
 
     auto family = alternate_space->family();
@@ -746,10 +713,7 @@ PDFErrorOr<NonnullRefPtr<SeparationColorSpace>> SeparationColorSpace::create(Doc
         return Error { Error::Type::MalformedPDF, "Separation color space has invalid alternate color space" };
 
     // "The tintTransform parameter must be a function"
-    auto param2 = TRY(document->resolve(parameters[2]));
+    auto tint_transform_object = TRY(document->resolve_to<Object>(parameters[2]));
-    if (!param2.has<NonnullRefPtr<Object>>())
-        return Error { Error::Type::MalformedPDF, "Separation color space expects object for third arg" };
-    auto tint_transform_object = param2.get<NonnullRefPtr<Object>>();
     auto tint_transform = TRY(Function::create(document, tint_transform_object));
 
     auto color_space = adopt_ref(*new SeparationColorSpace(move(alternate_space), move(tint_transform)));