From 8d937579737d1da707f08830da1dcaf1f6051ef1 Mon Sep 17 00:00:00 2001
From: Reuben Gardos Reid <5456207+ReubenJ@users.noreply.github.com>
Date: Fri, 19 Jan 2024 10:33:38 +0100
Subject: [PATCH 1/2] Add test to show `add_rule!` type coercion bug

Currently, the rule `true` is equivalent to the rule `1`.
This means that if one of them already exists in the grammar,
the new one is skipped.
---
 test/test_cfg.jl | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/test/test_cfg.jl b/test/test_cfg.jl
index 4b069b1..bdc7880 100644
--- a/test/test_cfg.jl
+++ b/test/test_cfg.jl
@@ -86,4 +86,28 @@
         rm("toy_pcfg.grammar")
     end
 
+    @testset "Test that strict equality is used during rule creation" begin
+        g₁ = @csgrammar begin
+            R = x
+            R = R + R
+        end
+
+        add_rule!(g₁, :(R = 1 | 2))
+
+        add_rule!(g₁,:(Bool = true))
+
+        @test all(g₁.rules .== [:x, :(R + R), 1, 2, true])
+
+        g₁ = @csgrammar begin
+            R = x
+            R = R + R
+        end
+
+        add_rule!(g₁,:(Bool = true))
+
+        add_rule!(g₁, :(R = 1 | 2))
+
+        @test all(g₁.rules .== [:x, :(R + R), true, 1, 2])
+    end
+
 end

From 5a031ff34259bda69841fefc736f3c74c72c833a Mon Sep 17 00:00:00 2001
From: Reuben Gardos Reid <5456207+ReubenJ@users.noreply.github.com>
Date: Fri, 19 Jan 2024 10:34:16 +0100
Subject: [PATCH 2/2] Use strict equality in `add_rule!`

Fixes #47.
---
 src/grammar_base.jl | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/grammar_base.jl b/src/grammar_base.jl
index d7be8f9..23a506c 100644
--- a/src/grammar_base.jl
+++ b/src/grammar_base.jl
@@ -211,13 +211,15 @@ function add_rule!(g::Grammar, e::Expr)
 		rvec = Any[]
 		parse_rule!(rvec, rule)
 		for r ∈ rvec
-			if r ∈ g.rules
-				continue
+			# Only add a rule if it does not exist yet. Check for existance
+			# with strict equality so that true and 1 are not considered
+			# equal. that means we can't use `in` or `∈` for equality checking.
+			if !any(r === rule for rule ∈ g.rules)
+				push!(g.rules, r)
+				push!(g.iseval, iseval(rule))
+				push!(g.types, s)
+				g.bytype[s] = push!(get(g.bytype, s, Int[]), length(g.rules))
 			end
-			push!(g.rules, r)
-			push!(g.iseval, iseval(rule))
-			push!(g.types, s)
-			g.bytype[s] = push!(get(g.bytype, s, Int[]), length(g.rules))
 		end
 	end
 	alltypes = collect(keys(g.bytype))