Add typecheck for insert! for #66

Add grammar to arguments to enable the check to be made.

src/HerbGrammar.jl

@@ -72,6 +72,8 @@ export
     read_pcsg,
     add_rule!,
     remove_rule!,
-    cleanup_removed_rules!
+    cleanup_removed_rules!,
+
+    RuleNodeTypeCheckError
 
 end # module HerbGrammar

src/nodelocation.jl

@@ -28,19 +28,34 @@ function Base.get(root::AbstractRuleNode, loc::NodeLoc)
     end
 end
 
+struct RuleNodeTypeCheckError <: Exception
+    message::String
+end
+
+Base.showerror(io::IO, e::RuleNodeTypeCheckError) = print(io, e.message)
 
 """
 insert!(loc::NodeLoc, rulenode::RuleNode)
 Replaces the subtree pointed to by loc with the given rulenode.
 """
-function Base.insert!(root::RuleNode, loc::NodeLoc, rulenode::RuleNode)
-    parent, i = loc.parent, loc.i
-    if loc.i > 0
-        parent.children[i] = rulenode
-    else
-        root.ind = rulenode.ind
-        root._val = rulenode._val
-        root.children = rulenode.children
-    end
-    return root
+function Base.insert!(root::RuleNode, loc::NodeLoc, rulenode::RuleNode, grammar::AbstractGrammar)
+	subtree = get(root, loc)
+	return_type_subtree 	  = return_type(grammar, subtree.ind)
+	return_type_replacement = return_type(grammar, rulenode.ind)
+	# if the types do not match throw an error
+	if return_type_replacement !== return_type_subtree 
+		throw(RuleNodeTypeCheckError("The provided replacement node does have the correct type to be replaced in the tree. 
+					The subtree of the current tree expects a rule with type $return_type_subtree , but 
+					the provided replacement has type $return_type_replacement"))
+	end
+
+	parent, i = loc.parent, loc.i
+	if loc.i > 0
+		parent.children[i] = rulenode
+	else
+		root.ind = rulenode.ind
+		root._val = rulenode._val
+		root.children = rulenode.children
+	end
+	return root
 end

test/test_rulenode_operators.jl

@@ -1,5 +1,5 @@
 module SomeDefinitions
-    a_variable_that_is_defined = 7
+a_variable_that_is_defined = 7
 end
 
 @testset verbose = true "RuleNode Operators" begin
@@ -15,4 +15,30 @@ end
         @test !isvariable(g₁, RuleNode(7, g₁), SomeDefinitions)
         @test isvariable(g₁, RuleNode(7, g₁))
     end
+    @testset "Check typecheck for insert!" begin
+        g = @cfgrammar begin
+            Start = Int + Int
+            Int = 1
+            Int = 2
+            B = "notgood"
+        end
+
+        root = RuleNode(1, [RuleNode(2), RuleNode(2)])  # 1 + 1
+        replacement = RuleNode(4)   # notgood 
+        @test rulenode2expr(replacement, g) == :("notgood")
+        location = NodeLoc(root, 1) # first child
+
+        # attempting to replace type Int by type B should not work
+        @test_throws HerbGrammar.RuleNodeTypeCheckError insert!(root, location, replacement, g)
+
+        root = RuleNode(1, [RuleNode(2), RuleNode(2)])  # 1 + 1
+        replacement = RuleNode(3)   # number 2 
+        @test rulenode2expr(replacement, g) == :2
+        location = NodeLoc(root, 1) # first child
+
+        # replacing from (1 + 1) -> (2 + 1) should work
+        insert!(root, location, replacement, g)
+
+        @test rulenode2expr(root, g) == :(2 + 1)
+    end
 end