Code to reproduce an upcasting compiler bug with Crystal 0.26.1

bug_upcasting.cr

module A
  abstract struct BaseFactory
    alias ValidContextTypes = A::Context

    def initialize(@context : ValidContextTypes)
    end
  end
end

module A
  struct Config
    alias Number = Float64 | Int64 | Int32
    alias AcceptedTypes = String.class | Number.class | Nil
    alias AcceptedFactories = BaseFactory.class | ::DummyFactory.class

    def initialize(@given_type : AcceptedTypes, @given_factory : AcceptedFactories)
    end

    def initialize_factory(context)
      @given_factory.new(context)
    end
  end
end

module A
  struct Context
    def input
      A::Value.new
    end
  end
end

module A
  struct Value
    def raw
      "raw"
    end
  end
end

require "spec"

struct ::DummyFactory < A::BaseFactory
end

describe A::Config do
  describe "Initialization" do
    it "can instantiate a FieldConfig" do
      klass = A::Config.new(given_type: String, given_factory: ::DummyFactory)
      klass.should be_a(A::Config)
    end
  end

  describe "#initialize_factory(context)" do
    it "initializes a factory with given context" do
      ctx = A::Context.new
      klass = A::Config.new(given_type: String, given_factory: ::DummyFactory).initialize_factory(ctx)
      klass.should be_a(DummyFactory)
    end
  end
end

console.txt

ljuti@Vanquish ~/Code/playground/crystal/upcasting $ crystal spec/upcasting_spec.cr
BUG: trying to upcast DummyFactory <- A::BaseFactory (Exception)
  from Crystal::CodeGenVisitor#upcast_distinct<LLVM::Value, Crystal::Type+, Crystal::Type+>:NoReturn
  from Crystal::CodeGenVisitor#upcast<LLVM::Value, Crystal::VirtualType, Crystal::Type+>:LLVM::Value
  from Crystal::CodeGenVisitor#codegen_primitive<Crystal::Call, Crystal::Primitive+, Crystal::Def+, Array(LLVM::Value)>:LLVM::Value
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#visit<Crystal::Assign>:(Bool | Nil)
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#codegen_fun<String, Crystal::Def+, Crystal::Type+, Bool, Crystal::CodeGenVisitor::ModuleInfo, Bool, Bool>:LLVM::Function
  from Crystal::CodeGenVisitor#target_def_fun<Crystal::Def+, Crystal::Type+>:LLVM::Function
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#codegen_fun<String, Crystal::Def+, Crystal::Type+, Bool, Crystal::CodeGenVisitor::ModuleInfo, Bool, Bool>:LLVM::Function
  from Crystal::CodeGenVisitor#target_def_fun<Crystal::Def+, Crystal::Type+>:LLVM::Function
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#visit<Crystal::Assign>:(Bool | Nil)
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#codegen_fun<String, Crystal::Def+, Crystal::Type+, Bool, Crystal::CodeGenVisitor::ModuleInfo, Bool, Bool>:LLVM::Function
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#codegen_fun<String, Crystal::Def+, Crystal::Type+, Bool, Crystal::CodeGenVisitor::ModuleInfo, Bool, Bool>:LLVM::Function
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#codegen_fun<String, Crystal::Def+, Crystal::Type+, Bool, Crystal::CodeGenVisitor::ModuleInfo, Bool, Bool>:LLVM::Function
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::CodeGenVisitor#visit<Crystal::Call>:Bool
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::CodeGenVisitor>:Nil
  from Crystal::Compiler#codegen<Crystal::Program, Crystal::ASTNode+, Array(Crystal::Compiler::Source), String>:(Tuple(Array(Crystal::Compiler::CompilationUnit), Array(String)) | Nil)
  from Crystal::Compiler#compile<Array(Crystal::Compiler::Source), String>:Crystal::Compiler::Result
  from Crystal::Command#run_command<Bool>:Nil
  from Crystal::Command#run:(Bool | Crystal::Compiler::Result | Nil)
  from main
Error: you've found a bug in the Crystal compiler. Please open an issue, including source code that will allow us to reproduce the bug: https://github.com/crystal-lang/crystal/issues