The bulk of this change is changing most pattern insts to be `Always`
rather than `AlwaysUnique` constants, so that they can be wrapped in
`SpecificConstant`s to perform substitution. That then lets thunking
rely much more on `SpecificConstant` wrappers instead of deep-copying
the inst tree with modified types.
This approach to thunking should scale better, particularly as things
like form generics make function signatures more complex, because we can
leverage the existing support for constant evaluation and substitution.
Unfortunately, applying this approach to binding patterns will require
more work; see the TODO near the top of `thunk.cpp` for details.
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Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Fix import logic to make all imported packages be children of the
`NameScopeId::Package` scope. Previously, indirectly-imported packages
would end up as children of their importing package's scope, which
resulted in them not being treated as packages at all, and in particular
not being fingerprinted as packages.
Fixing that caused a failure in the fingerprinting logic as we started
to encounter packages with no correspoding import scopes. Instead of
looking for import scopes, use a simpler mechanism to map packages to
their package names, and clean up.
Unfortunately the latter change churns all the fingerprints again :(
Hopefully this is the last time for a while.
Add `ExportVarToCpp`. This checks the `clang_decls` mapping and returns
an existing decl if found. Otherwise, it creates a new `VarDecl` and
adds it to the `clang_decls` mapping.
When lowering, in `FileContext::BuildGlobalVariableDecl`, the
`clang_decls` mapping is used to lookup an existing
`llvm::GlobalVariable` for the instruction. If found, use that rather
than creating a new one to avoid an unwanted second definition in the
llvm IR.
Geoff Romer
Nicholas Bishop