From d9abcff39a907c10569a75e2df1bba843db202ba Mon Sep 17 00:00:00 2001
From: thorimur <68410468+thorimur@users.noreply.github.com>
Date: Wed, 20 Sep 2023 14:17:39 -0400
Subject: [PATCH] feat: fail if `suggestions` is empty

---
 Std/Tactic/TryThis.lean | 1 +
 test/tryThis.lean       | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/Std/Tactic/TryThis.lean b/Std/Tactic/TryThis.lean
index 33fafbe4ec..eb2cf0f911 100644
--- a/Std/Tactic/TryThis.lean
+++ b/Std/Tactic/TryThis.lean
@@ -428,6 +428,7 @@ The parameters are:
 def addSuggestions (ref : Syntax) (suggestions : Array Suggestion)
     (origSpan? : Option Syntax := none)
     (header : String := "Try these:") : MetaM Unit := do
+  if suggestions.isEmpty then throwErrorAt ref "no suggestions available"
   let msgs := suggestions.map toMessageData
   let msgs := msgs.foldl (init := MessageData.nil) (fun msg m => msg ++ m!"\n• " ++ m)
   logInfoAt ref m!"{header}{msgs}"
diff --git a/test/tryThis.lean b/test/tryThis.lean
index 32d45c02c9..e012ec8242 100644
--- a/test/tryThis.lean
+++ b/test/tryThis.lean
@@ -186,3 +186,7 @@ info: Grab bag:
     postInfo? := " at 0.166667.",
     style? := some (.value (1/6))}
 ] with_header "Grab bag:"
+
+/-- error: no suggestions available -/
+#guard_msgs in
+#demo #[]