Add docs to enum member helper methods (#15379)

spec/compiler/semantic/enum_spec.cr

@@ -613,4 +613,28 @@ describe "Semantic: enum" do
     a_def = result.program.types["Foo"].lookup_defs("foo").first
     a_def.previous.should be_nil
   end
+
+  it "adds docs to helper methods" do
+    result = top_level_semantic <<-CRYSTAL, wants_doc: true
+    enum Foo
+      # These are the docs for `Bar`
+      Bar = 1
+    end
+    CRYSTAL
+
+    a_defs = result.program.types["Foo"].lookup_defs("bar?")
+    a_defs.first.doc.should eq("Returns `true` if this enum value equals `Bar`")
+  end
+
+  it "marks helper methods with `:nodoc:` if the member is `:nodoc:`" do
+    result = top_level_semantic <<-CRYSTAL, wants_doc: true
+    enum Foo
+      # :nodoc:
+      Bar = 1
+    end
+    CRYSTAL
+
+    a_defs = result.program.types["Foo"].lookup_defs("bar?")
+    a_defs.first.doc.should eq(":nodoc:")
+  end
 end

src/compiler/crystal/semantic/top_level_visitor.cr

@@ -824,6 +824,13 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
     method_name = is_flags ? "includes?" : "=="
     body = Call.new(Var.new("self").at(member), method_name, Path.new(member.name).at(member)).at(member)
     a_def = Def.new("#{member.name.underscore}?", body: body).at(member)
+
+    a_def.doc = if member.doc.try &.starts_with?(":nodoc:")
+                  ":nodoc:"
+                else
+                  "Returns `true` if this enum value #{is_flags ? "contains" : "equals"} `#{member.name}`"
+                end
+
     enum_type.add_def a_def
   end