ymandel added a comment.
Thanks for looping me in. I'll try to take a detailed look later today. In the
meantime, I'll note that we have something similar internally which I never got
around to upstreaming. However, we chose to support arbitrarily many matchers,
with this interface:
const clang::ast_matchers::internal::VariadicFunction<
clang::ast_matchers::internal::Matcher<clang::CompoundStmt>,
internal::SequenceMatcher<clang::Stmt>,
internal::hasSubstatementSequenceFunc>
hasSubstatementSequence = {};
The `SequenceMatcher` API is:
// The following definitions all support the `hasSubstatementSequence`
// matcher. This matcher supports describing the series of statements in a
// compound statement, in a style inspired by regular expressions. Unlike
// regular expressions, however, these operators are deterministic. Choices
are
// tried in order. For optional-style operators (`maybeOne`, `zeroOrMore` and
// `oneOrMore`) the positive choice is considered first.
template <typename T>
internal::SequenceMatcher<T> exactlyOne(
clang::ast_matchers::internal::Matcher<T> Matcher) {
return {std::move(Matcher)};
}
template <typename T>
internal::SequenceMatcher<T> maybeOne(
clang::ast_matchers::internal::Matcher<T> Matcher) {
return {internal::SequenceElementKind::ZeroOrOne, std::move(Matcher)};
}
template <typename T>
internal::SequenceMatcher<T> zeroOrMore(
clang::ast_matchers::internal::Matcher<T> Matcher) {
return {internal::SequenceElementKind::ZeroOrMore, std::move(Matcher)};
}
template <typename T>
internal::SequenceMatcher<T> oneOrMore(
clang::ast_matchers::internal::Matcher<T> Matcher) {
return {internal::SequenceElementKind::OneOrMore, std::move(Matcher)};
}
I also implemented a non-deterministic version using backtracking. But, that
scared me off because of its potential cost (potential, b/c we could use
memoization like packrat parsing to avoid the exponential).
That said, my experience indicates that once you're thinking in terms of
sequences, you're probably going to find that you want to match over the CFG,
rather than the AST directly.
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https://reviews.llvm.org/D116518/new/
https://reviews.llvm.org/D116518
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