std::optional::value() has undesired exception checking semantics and is
unavailable in older Xcode (see _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS). The
call sites block std::optional migration.
This makes `ninja check-clang` work in the absence of llvm::Optional::value.
Currently, our boolean formulas (`BoolValue`) don't form a lattice, since they
have no Top element. This patch adds such an element, thereby "completing" the
built-in model of bools to be a proper semi-lattice. It still has infinite
height, which is its own problem, but that can be solved separately, through
widening and the like.
Patch 1 for Issue #56931.
Differential Revision: https://reviews.llvm.org/D135397
Previously we used to desugar implications and biconditionals into
equivalent CNF/DNF as soon as possible. However, this desugaring makes
debug output (Environment::dump()) less readable than it could be.
Therefore, it makes sense to keep the sugared representation of a
boolean formula, and desugar it in the solver.
Reviewed By: sgatev, xazax.hun, wyt
Differential Revision: https://reviews.llvm.org/D130519
