Repro

.github/workflows/repro.yml

@@ -0,0 +1,18 @@
+name: Repro
+on: [push]
+
+permissions:
+  contents: read
+
+jobs:
+  install:
+    name: Rust 1.80
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./
+        with:
+          toolchain: 1.80
+      - run: rustup toolchain list
+      - run: rustc --version

action.yml

@@ -30,6 +30,8 @@ outputs:
 runs:
   using: composite
   steps:
+    - run: echo '${{toJSON(inputs.toolchain)}}'
+
     - id: parse
       run: |
         : parse toolchain version