Add assertion for decreasing the indent

Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
(cherry picked from commit a27651908fc1b5ef73a81e46434a408c5868fa7b)
Change-Id: I2ec78e234c1c6e982f7b05f81d8b8356daf6c274

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index 53d0861bf..76f9a9c56 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -174,6 +174,7 @@ private:
     void decreaseIndent()
     {
         if (options.prettyPrint()) {
+            assert(indent.size() >= options.prettyIndent);
             indent.resize(indent.size() - options.prettyIndent);
         }
     }