Fix crystal tool format visiting circular hierarchies

straight-shoota · Oct 7, 2024 · d2305f8 · d2305f8
1 parent 1f6b51d
commit d2305f8
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diff --git a/spec/compiler/crystal/tools/unreachable_spec.cr b/spec/compiler/crystal/tools/unreachable_spec.cr
@@ -112,6 +112,14 @@ describe "unreachable" do
       CRYSTAL
   end
 
+  it "handles circular hierarchy references (#14034)" do
+    assert_unreachable <<-CRYSTAL
+      class Foo
+        alias Bar = Foo
+      end
+      CRYSTAL
+  end
+
   it "finds initializer" do
     assert_unreachable <<-CRYSTAL
       class Foo

diff --git a/src/compiler/crystal/tools/unreachable.cr b/src/compiler/crystal/tools/unreachable.cr
@@ -128,6 +128,15 @@ module Crystal
     property excludes = [] of String
 
     def process_type(type)
+      # Avoid visiting circular hierarchies. There's no use in processing
+      # alias types anyway.
+      # For example:
+      #
+      #     struct Foo
+      #        alias Bar = Foo
+      #     end
+      return if type.is_a?(AliasType) || type.is_a?(TypeDefType)
+
       if type.is_a?(ModuleType)
         track_unused_defs type
       end