add a transcript test to close #873

unison-src/transcripts/check873.md

@@ -0,0 +1,13 @@
+See [this ticket](https://github.com/unisonweb/unison/issues/873); the point being, this shouldn't crash the runtime. :)
+
+```unison
+(-) = builtin.Nat.sub
+```
+
+```ucm
+.> add
+```
+
+```unison
+baz x = x - 1
+```

unison-src/transcripts/check873.output.md

@@ -0,0 +1,46 @@
+See [this ticket](https://github.com/unisonweb/unison/issues/873); the point being, this shouldn't crash the runtime. :)
+
+```unison
+(-) = builtin.Nat.sub
+```
+
+```ucm
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      - : builtin.Nat -> builtin.Nat -> builtin.Int
+   
+  Now evaluating any watch expressions (lines starting with
+  `>`)... Ctrl+C cancels.
+
+```
+```ucm
+.> add
+
+  ⍟ I've added these definitions:
+  
+    - : builtin.Nat -> builtin.Nat -> builtin.Int
+
+```
+```unison
+baz x = x - 1
+```
+
+```ucm
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      baz : builtin.Nat -> builtin.Int
+   
+  Now evaluating any watch expressions (lines starting with
+  `>`)... Ctrl+C cancels.
+
+```