feat: quotation precheck for choice nodes

src/Lean/Elab/Quotation/Precheck.lean

@@ -128,6 +128,14 @@ private def isSectionVariable (e : Expr) : TermElabM Bool := do
     es.getElems.forM precheck
   | _ => throwUnsupportedSyntax
 
+@[builtinQuotPrecheck choice] def precheckChoice : Precheck := fun stx => do
+  let checks ← stx.getArgs.mapM (_root_.observing ∘ precheck)
+  let fails := checks.zip stx.getArgs |>.filterMap fun
+    | (.error e, stx) => some m!"{stx}\n{e.toMessageData}"
+    | _               => none
+  unless fails.isEmpty do
+    throwErrorAt stx "ambiguous notation with at least one interpretation that failed quotation precheck, possible interpretations {indentD (MessageData.joinSep fails.toList m!"\n\n")}"
+
 @[builtinTermElab precheckedQuot] def elabPrecheckedQuot : TermElab := fun stx expectedType? => do
   let singleQuot := stx[1]
   runPrecheck singleQuot.getQuotContent

tests/lean/notationPrecheck.lean

@@ -3,6 +3,11 @@ notation "a" => fun x => a
 syntax "b" term : term
 notation "c" => b x
 
-set_option quotPrecheck false
+set_option quotPrecheck false in
 notation "d" => b x
 #check d
+
+infix:10 " ∧ " => and
+set_option pp.raw true
+notation "foo" => fun x y => x ∧ y
+notation "bar" => fun x => x ∧ y

tests/lean/notationPrecheck.lean.expected.out

@@ -4,3 +4,9 @@ notationPrecheck.lean:4:16-4:19: error: no macro or `[quotPrecheck]` instance fo
 This means we cannot eagerly check your notation/quotation for unbound identifiers; you can use `set_option quotPrecheck false` to disable this check.
 notationPrecheck.lean:8:7-8:8: error: elaboration function for 'termB_' has not been implemented
   b x✝
+notationPrecheck.lean:13:27-13:32: error: ambiguous notation with at least one interpretation that failed quotation precheck, possible interpretations 
+  («term_∧__1» `x "∧" `y)
+  unknown identifier 'y' at quotation precheck; you can use `set_option quotPrecheck false` to disable this check.
+  
+  («term_∧_» `x "∧" `y)
+  unknown identifier 'y' at quotation precheck; you can use `set_option quotPrecheck false` to disable this check.