From 856f7d3d3ab9d32ca2a920ae394d24cf4136e588 Mon Sep 17 00:00:00 2001
From: Mirek Kratochvil <miroslav.kratochvil@uni.lu>
Date: Thu, 17 Aug 2023 09:25:57 +0200
Subject: [PATCH] add a test for the unreachable clause reporting

---
 test/clauses.jl | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/test/clauses.jl b/test/clauses.jl
index 79f1c3e..e60fb14 100644
--- a/test/clauses.jl
+++ b/test/clauses.jl
@@ -90,6 +90,27 @@ end
     @test_throws DomainError P.flatten(rules, Char)
 end
 
+@testset "Unreachable rules are reported" begin
+    rules = Dict(:xxx => P.seq(:yyy, P.fail), :yyy => P.epsilon, :zzz => P.epsilon)
+
+    @test_throws ErrorException P.make_grammar([:xxx], P.flatten(rules, Char))
+    @test begin
+        # this should simply not throw anything
+        P.make_grammar([:xxx, :zzz], P.flatten(rules, Char))
+        true
+    end
+
+    @test try
+        P.make_grammar([:xxx], P.flatten(rules, Char))
+    catch e
+        b = IOBuffer()
+        showerror(b, e)
+        errorstring = String(take!(b))
+
+        (occursin(":zzz", errorstring) && all(!occursin(errorstring), [":xxx", ":yyy"]))
+    end
+end
+
 @testset "Corner-case epsilon matches" begin
     str = "whateveρ"