Previously the Clone() of the AST would clone all the functions, globals
and type declarations in a temporary vector, then assign this to the
ast::Module. This meant that adding new module-scope declarations inside
callbacks of ReplaceAll() would place them right at the top, before any
of the cloned declarations.
As top-level declarations are not statements, ensuring that a new object
comes before the current ReplaceAll() declaration is surprisingly
tricky.
With this change, we can now safely assume that calling
ProgramBuilder::Var(), ProgramBuilder::Func(), ProgramBuilder::Alias()
or ProgramBuilder::Structure() inside a ReplaceAll() will add that
module-scoped declaration before the currently processed top-level
declaration.
Change-Id: I52772fdc85940c8ac8d941fbd53374a4dd64a9f4
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54320
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
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