Fix `str.replace_re` and `str.replace_re_all` (#6615)

Fixes #6057. The reductions of `str.replace_re` and `str.replace_re_all`
were not correctly enforcing that the operations replace the _first_
occurrence of some regular expression in a string. This commit fixes the
issue by introducing a new operator `str.indexof_re(s, r, n)`, which,
analoguously to `str.indexof`, returns the index of the first match of
the regular expression `r` in `s`. The commit adds basic rewrites for
evaluating the operator as well as its reduction. Additionally, it
converts the reductions of `str.replace_re` and `str.replace_re_all` to
use that new operator. This simplifies the reductions of the two
operators and ensures that the semantics are consistent between the two.

1 files changed, 10 insertions, 0 deletions

diff --git a/test/regress/regress1/strings/issue6337-replace-re-all.smt2 b/test/regress/regress1/strings/issue6337-replace-re-all.smt2
new file mode 100644
index 000000000..9ae168b63
--- /dev/null
+++ b/test/regress/regress1/strings/issue6337-replace-re-all.smt2
@@ -0,0 +1,10 @@
+; COMMAND-LINE: --strings-exp
+(set-logic QF_SLIA)
+(declare-fun str3 () String)
+(declare-fun str8 () String)
+(declare-fun str12 () String)
+(declare-fun str14 () String)
+(declare-fun str15 () String)
+(assert (distinct str15 (str.++ str14 str3 str8 str14) (str.replace_re_all str12 (re.comp (str.to_re str15)) (str.++ str14 str3 str8 str14)) str12))
+(set-info :status sat)
+(check-sat)