Fix metavar detection false negative

1 files changed, 2 insertions, 5 deletions

diff --git a/lib/Core/ExecutionState.cpp b/lib/Core/ExecutionState.cpp
index 270a3e16..1e45812c 100644
--- a/lib/Core/ExecutionState.cpp
+++ b/lib/Core/ExecutionState.cpp
@@ -415,12 +415,9 @@ std::string extractMetaEnvVar(ref<Expr> e) {
   }
 
   const auto& name = read->updates.root->name;
-  // string::starts_with requires C++20
-  if (name.substr(0, 8) != "__choose")
+  // Skip __choose\d.*
+  if (name.substr(0, 8) != "__choose" || '0' > name[8] || name[8] > '9')
     return "";
-  for (const auto c : name.substr(8))
-    if ('0' > c || c > '9')
-      return "";
   std::string value;
   constant->toString(value);
   return "__SWITCH" + name.substr(8, name.size() - 8) + "=" + value;