# What: replace a default repository set by its documented repository name.
# Why: changing the exec triple (for example, MSVC to gnullvm) also changes the
# lookup key, so matching by both the old triple and name leaves the default
# toolchain registered and lets it win toolchain resolution.

diff --git a/rust/extensions.bzl b/rust/extensions.bzl
--- a/rust/extensions.bzl
+++ b/rust/extensions.bzl
@@ -100,8 +100,13 @@ def _rust_impl(module_ctx):
             **repository_set
         )
         extra_toolchain_infos.update(**toolchain_infos)
-        if toolchain_triples.get(repository_set["exec_triple"]) == repository_set["name"]:
-            toolchain_triples.pop(repository_set["exec_triple"], None)
+        replaced_exec_triples = [
+            exec_triple
+            for exec_triple, name in toolchain_triples.items()
+            if name == repository_set["name"]
+        ]
+        for exec_triple in replaced_exec_triples:
+            toolchain_triples.pop(exec_triple)
 
     toolchains = root.tags.toolchain
     if not toolchains and rules_rust: