Two of the defects reported on issue #2253 come from the decompiler
writing text that means something else when it is read again.
A markup extension is written as a single attribute value, and its
grammar gives ',' '=' '{' '}' and the quote characters a meaning. Values
went out unquoted, so an argument carrying any of them was read back as
further name/value pairs: {DXBinding Expr='Price - Prev > 0 ? ...'}, the
reported case, no longer compiles at all (MC3042, MC3045). Values without
such a character stay unquoted, because quoting them would rewrite every
document that never needed it.
A clr-namespace declaration names the CLR namespace it maps, but nothing
read that name out of it, so no lookup by namespace could match a
declaration the document itself had made. Every type in such a namespace
then got a second prefix declared on the element that used it. The
assembly is the second half of the same lookup, and there the document
records the name it was written against while a well-known type carries
the assembly it resolves to now - "mscorlib" against
"System.Private.CoreLib" - so the two are also accepted as the same when
the recorded assembly forwards the type.
Assisted-by: Claude:claude-opus-5:Claude Code
Obfuscators put arbitrary characters into BAML strings, and XML 1.0 has no
representation for most control characters - a numeric character reference is invalid
for them too. Writing such a document threw ArgumentException from XmlWriter, which
loses the resource on project export and shows an exception instead of the page in the
UI. The escapes are spelled the way the C# output spells them, so one convention covers
both languages. Namespace URIs have to be escaped where the XNamespace is created rather
than in the final pass: the URI is baked into every element name built from it, so
patching only the xmlns declaration would desync the two. Characters XML can carry stay
untouched, so ordinary documents decompile byte-identically.
Every BAML stream of an assembly lives in one .resources container, and the recovery
around resource writing sat outside the loop over its entries, so a single page that
could not be written discarded every other page sharing the container with it.
Assisted-by: Claude:claude-opus-5:Claude Code
An assembly can map one CLR namespace to several XML namespaces: PresentationFramework
maps its namespaces to both the winfx/2006 and the netfx/2007 presentation namespace. The
fallback used when the BAML xmlns records name no namespace for a type always preferred the
winfx/2006 one, so a document that binds the default prefix to netfx/2007 ended up with a
root start tag that declares one presentation namespace and needs the other for its own
name, which XmlWriter rejects. Only the root carries the xmlns declaration, which is why
skipping XClassRewritePass worked around it.
Assisted-by: Claude:claude-opus-5:Claude Code
Siegfried Pammer
Peter Crabtree
Christoph Wille
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