swift

866e6286 - Sema: Fix availability checking in function default argument closure expressions.

Sema: Fix availability checking in function default argument closure expressions. When building the TypeRefinementContext tree, delay pushing a decl's body context until the body Stmt is actually encountered by the `ASTWalker`. This ensures that default argument expressions do not automatically inherit the availability context of the function body. Resolves rdar://95148645