理論から入門するswift/lib/Sema - わいわいswiftc #1

https://iosdiscord.connpass.com/event/82436/
での発表資料です。

Transcript

1. ཧ࿦͔Βೖ໳͢Δ
   swift/lib/Sema
   Θ͍Θ͍swiftc #1
   @ukitaka
   

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2. twitter: @ukitaka_
   github: @ukitaka
   Yuki Takahashi
   

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3. ࣗݾ঺հ
   ❤ ؔ਺ܕϓϩάϥϛϯάɺDDD
   ✏ ܕγεςϜɺίϯύΠϥ
   ௿ϨΠϠʔ
   

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4. ϒϩάॻ͍ͯΔ
   https://blog.waft.me
   

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5. ษڧ͕ͯΒ࡞ͬͨ΋ͷ
   • SwiftͰܕγεςϜ / ܕਪ࿦Λॻ͍ͯΈͨΓ
   • ukitaka/TypeSystems
   • ukitaka/AlgorithmW.swift
   • SILOptimizerΛࣗ࡞ͯ͠ΈͨΓ
   • ukitaka/sil-opt-scala
   

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6. contribute͸…
   

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7. ࣗݾ঺հऴΘΓ
   

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8. ࠓ೔ͷ࿩
   

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9. swift/lib/Sema
   

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10. swift/lib/Sema
    • Sema = Semantic Analysis (ҙຯղੳ)
    • ओʹܕਪ࿦ɾܕݕࠪΛ୲౰͢ΔϞδϡʔϧ
    • ίʔυྔҰ൪ଟ͍
    • ΊͪΌΊͪΌෳࡶ
    

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11. ܕͷ࿩ָͦ͠͏…Ͱ΋
    Ͳ͔͜ΒखΛ෇͚Α͏…
    

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12. swift/lib/Sema
    • ෳࡶʹབྷΈ߹ͬͯ͸͍Δ͕ɺ͍͔ͭ͘ͷτϐο
    Ϋͷू·Γɻͦͯ͠୯ମͰݟΔͱཧ࿦௨Γ࣮
    ૷͞Ε͍ͯΔ৔߹͕ଟ͍ɻ
    • ֓೦Λ஌͍ͬͯΔ͚ͩͰ΋͍ͩͿೖΓ΍͍͢
    • ͳͷͰ… ʮཧ࿦͔Βೖ໳͢Δʯ
    

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13. ࠓ೔ѻ͏τϐοΫ
    • δΣωϦοΫͳؔ਺ (letଟ૬)ͱܕਪ࿦
    • αϒλΠϐϯάͱܕڧ੍ҙຯ࿦
    • ଘࡏܕ (࣌ؒͷ౎߹Ͱলུ)
    

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14. ଘࡏܕͷղઆ͸QiitaͰ…
    

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15. δΣωϦοΫͳؔ਺(letଟ૬)
    ͱܕਪ࿦
    

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16. Generics in Swift
    • δΣωϦΫεपΓͷ࣮૷͸ͱʹ͔͘೉͍͠…
    • ͔͠͠(੍໿Λؚ·ͳ͍)δΣωϦοΫͳؔ਺ͩ
    ͚ͳΒܕਪ࿦ؚΊཧ࿦΋࣮૷΋ͦΜͳʹ೉͘͠
    ͳ͍
    • δΣωϦοΫͳؔ਺ͱͦͷܕਪ࿦ΛݟΔ͜ͱͰɺ
    SemaϞδϡʔϧΛ၆ᛌ͢Δ
    

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17. δΣωϦοΫͳؔ਺
    

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18. = ଟ૬ͳؔ਺
    

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19. ଟ૬ੑͱ͸…
    

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20. ଟ૬ੑ(polymorphism)
    • ϓϩάϥϜͷҰ෦෼ΛɺҟͳΔจ຺Ͱ͸ҟͳ
    Δܕͱͯ͠༻͍Δ͜ͱΛՄೳʹ͢Δ֤छݴޠ
    ػೳ
    

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21. ଟ૬ੑ(polymorphism)
    Bool → Bool
    ಉ͡idؔ਺Ͱ΋ɺҟͳΔจ຺Ͱ͸ҟͳΔܕ
    Int → Int
    

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22. ଟ૬ͳؔ਺͸SwiftͰ͸
    Ͳ͏࣮ݱ͞Ε͍ͯΔʁ
    

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23. ଟ૬ͳؔ਺ͱܕਪ࿦
    • ࣮͸ଟ૬ͳؔ਺ͱܕਪ࿦͸͋ΔҙຯηοτͰ
    ఏڙ͞Ε͍ͯΔػೳ
    • ܕਪ࿦Λ࢖ͬͯϙϦϞʔϑΟζϜΛ࣮ݱ
    • δΣωϦοΫͳؔ਺Λ஌Δʹ͸ܕਪ࿦΋஌Δ
    ඞཁ͕͋Δ
    

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24. Swiftʹ͓͚Δ
    (ϩʔΧϧ)ܕਪ࿦
    

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25. ܕਪ࿦ͷେ·͔ͳྲྀΕ
    1. ܕ͕໌ࣔ͞Ε͍ͯͳ͍ͱ͜ΖΛܕม਺(Type
    Variable)Ͱ͓͘
    2. ܕม਺ͷ੍໿(Constraint)Λੜ੒͢Δ
    3. ੍໿Λղ͘
    

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26. ܕਪ࿦ͷେ·͔ͳྲྀΕ
    • ܕ͕ܾ·͍ͬͯͳ͍ͱ͜ΖΛܕม਺Ͱ͓͘
    Type Variables:
    #0 = $T0 [inout allowed]
    #1 = $T1 [inout allowed]
    $ swift -frontend -typecheck -debug-constraints test.swift
    $T1 $T0
    

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27. • ੍໿(Constraint)Λੜ੒͢Δ
    ܕਪ࿦ͷେ·͔ͳྲྀΕ
    $T0 literal conforms to ExpressibleByIntegerLiteral
    $T0 conv $T1
    $ swift -frontend -typecheck -debug-constraints test.swift
    $T0 ͸੔਺Ϧςϥϧ
    $T0 ͸$T1ʹม׵Ͱ͖Δ
    

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28. ܕਪ࿦ͷେ·͔ͳྲྀΕ
    • ੍໿Λղ͘
    Active bindings: $T0 := Int
    (trying $T0 := Int
    ($T1 bindings=(supertypes of) Int)
    Active bindings: $T1 := Int
    (trying $T1 := Int
    (found solution 0 0 0 0 0 0 0 0 0 0 0 0 0)
    )
    )
    $ swift -frontend -typecheck -debug-constraints test.swift
    

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29. ܕਪ࿦ͷେ·͔ͳྲྀΕ
    • ੍໿Λղ͘
    ---Solution---
    Fixed score: 0 0 0 0 0 0 0 0 0 0 0 0 0
    Type variables:
    $T1 as Int
    $T0 as Int
    $ swift -frontend -typecheck -debug-constraints test.swift
    Int Int
    

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30. δΣωϦοΫͳؔ਺ͷ৔߹
    

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31. ܕਪ࿦ͷେ·͔ͳྲྀΕ(࠶ܝ)
    1. ܕ͕໌ࣔ͞Ε͍ͯͳ͍ͱ͜ΖΛܕม਺(Type
    Variable)Ͱ͓͘ ←ଟ૬ͳؔ਺ͷ࣮ݱʹ͸͜͜ʹϙΠϯτ
    2. ܕม਺ͷ੍໿(Constraint)Λੜ੒͢Δ
    3. ੍໿Λղ͘
    

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32. δΣωϦοΫͳؔ਺ͷܕਪ࿦
    

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33. δΣωϦοΫͳؔ਺ͷܕਪ࿦
    ಺෦తͳܕͷදݱ: <τ_0_0> τ_0_0 → τ_0_0
    ݟͨ໨ͷܕ: A → A
    Aͱ͍͏໊લ͸ࣺͯΒΕͯdepthͱindexʹΑΔ໊ແ͠දݱʹͳ͍ͬͯΔ
    

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34. δΣωϦοΫͳؔ਺ͷܕਪ࿦
    ग़ݱͷͨͼʹτ_0_0ʹ৽͍͠ܕม਺ΛׂΓ౰ͯΔ
    Opened types:
    opens τ_0_0 -> $T1
    opens τ_0_0 -> $T4
    $ swift -frontend -typecheck -debug-constraints test.swift
    ͜Ε͕ଟ૬ੑΛ࣮ݱ͍ͯ͠ΔϙΠϯτ
    $T1 -> $T1 $T4 -> $T4
    

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35. δΣωϦοΫͳؔ਺ͷܕਪ࿦
    Type Variables:
    #0 = $T0 as ($T1) -> $T1
    #1 = $T1
    #2 = $T2
    #3 = $T3 as ($T4) -> $T4
    #4 = $T4
    #5 = $T5
    #6 = $T6
    $ swift -frontend -typecheck -debug-constraints test.swift
    

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36. δΣωϦοΫͳؔ਺ͷܕਪ࿦
    • ͋ͱ͸ಉ͡Α͏ʹ੍໿ੜ੒ͯ͠ղ͚ͩ͘
    ---Solution---
    Fixed score: 0 0 0 0 0 0 0 0 0 0 0 0 0
    Type variables:
    $T6 as (Int, Bool)
    $T3 as (Bool) -> Bool
    $T4 as Bool
    $T0 as (Int) -> Int
    $T1 as Int
    $T5 as Bool
    $T2 as Int
    $ swift -frontend -typecheck -debug-constraints test.swift
    

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37. δΣωϦοΫͳؔ਺ͷܕਪ࿦
    • ग़ݱͷͨͼʹ৽͍͠ܕม਺ΛׂΓ౰্ͯͨͰɺ
    ܕΛਪ࿦͢Δ͜ͱʹΑͬͯଟ૬ੑΛ࣮ݱͯ͠
    ͍Δɻ
    • ͜ΕΛletଟ૬ͱݺͿ
    

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38. δΣωϦοΫͳؔ਺ͱܕਪ࿦
    The secret life of types in Swift
    https://medium.com/@slavapestov/the-secret-life-of-types-in-swift-ff83c3c000a5
    

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39. ΋͏গ࣮͠૷دΓͷ࿩
    

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40. ܕνΣοΫؔ࿈ͷओཁͳΫϥε
    • ίʔυྔଟ͍͚ͲɺओͳΫϥε͸2ͭͷΈ
    • TypeChecker → ܕݕࠪ୲౰
    • ConstraintSystem → ܕਪ࿦୲౰
    • TypeChecker͕Expr͝ͱʹConstraintSystemΛ
    ΠϯελϯεԽͯ͠࢖͍ͬͯΔΠϝʔδ
    

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41. TypeChecker / ConstraintSystem
    

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42. ܕม਺ɺ੍໿ੜ੒ͷྫ
    

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43. ੍໿ͷ୯ҰԽ (solve)
    

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44. ੍໿ͷ୯ҰԽ (solve)
    • جຊతʹ͸ީิΛͲΜͲΜࢼ͍ͯ͘͠
    • PotentialBindings ( e.g. ੔਺Ϧςϥϧ͔ͩΒIntͩΖ͏ )
    • Overloadͷީิͨͪ
    • ConstraintGraphͱ͍͏(ϋΠύʔ)άϥϑͰ੍໿
    Λ؅ཧ
    • େ·͔ʹ͸BindingΛ௥Ճ → άϥϑΛ੔ཧͷ܁Γฦ͠
    

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45. ղͷద༻(apply)ͱASTॻ͖׵͑
    • ExprRewriter͕ܕ෇͖ͷAST΁ͱॻ͖׵͑Δ
    

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46. letଟ૬Λ࣮ݱ͍ͯ͠Δ෦෼
    δΣωϦοΫͳؔ਺ͳΒ
    ܕύϥϝʔλʹ
    ϑϨογϡͳܕม਺Λ
    ׂΓ౰ͯΔͱ͍͏
    ཧ࿦ͦͷ··ͷ࣮૷ɻ
    

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47. ·ͱΊ
    • ଟ૬ͳؔ਺͕ܕਪ࿦ʹΑ࣮ͬͯݱ͞Ε͍ͯΔ
    ༷ࢠΛݟͨ
    • ConstraintSystem͕ܕਪ࿦Λ͢Δͷେ·͔ͳ
    ྲྀΕΛΈͨ
    

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48. ͓·͚: ੍໿෇͖ͷδΣωϦΫε͸ʁ
    • ࣮૷ͱͯ͠͸جຊతʹ͸ಉ͡
    • TʹׂΓ౰ͯΒΕͨܕม਺ʹ $T1 conforms to
    EquatableͷΑ͏ͳ੍໿͕ՃΘΔ͘Β͍
    • ͔͠͠എܠʹ͋Δཧ࿦͸·ͨผ…
    

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49. ͓·͚: ੍໿෇͖ͷδΣωϦΫε͸ʁ
    • ݶఆܕ (Qualified type)
    • TaPLʹ͸໊લ͔͠ࡌͬͯͳ͍
    • Jones, Mark P. Qualified Types: Theory and Practice. Cambridge
    University Press, 1994.
    • Haskellͷ Eq a => a -> a -> Bool
    • ༗քྔԽ(bounded qualification)Ͱ͸ͳ͍
    

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50. αϒλΠϐϯάͱ
    ܕڧ੍ҙຯ࿦
    

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51. ΫΠζ
    • Swiftʹ͓͍ͯɺT͸ OptionalͷαϒλΠ
    ϓ͔ʁʁ
    

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52. T is subtype of Optional
    • ౴͑: αϒλΠϓɻ
    • αϒλΠϐϯάنଇ͸υΩϡϝϯτʹ͸ॻ͍
    ͍ͯͳ͍͕ɺιʔείʔυதͷίϝϯτʹͪΐ
    ͪ͜ΐ͜ఆٛ͞Ε͍ͯΔɻ(͢΂͕ͯॻ͍ͯ͋ΔΘ͚
    Ͱ͸ͳ͍)
    • lib/Sema/CSSimplify.cpp Λࢀর
    

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53. T is subtype of Optional
    

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54. αϒλΠϓؔ܎
    • ͲΜͳαϒλΠϓؔ܎Λ࣋ͨͤΔ͔͸ͦͷݴޠͰ
    ͷܾΊͷ໰୊
    • ྫ͑͹ Int < Float ͱ͔ Int < String ͱ͔࣋ͨͤͯ
    ΋(੔߹ੑ͕औΕΔͷͳΒ) ྑ͍
    • Swift͸OptionalΛָʹѻ͏࢓૊Έͱͯ͠ ɺ
    T < OptionalΛ࠾༻͍ͯ͠Δ
    

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55. ଞʹ͸ͲΜͳ
    αϒλΠϓؔ܎͕͋Δʁ
    

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56. Optional-to-optional
    

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57. Metatype
    

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58. Existential
    

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59. αϒλΠϓ͔ͩΒ
    ͳΜͰ΋OKʁ
    

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60. ྫ: Existential
    

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61. ࣮ߦ࣌ͷϝϞϦ্ͷදݱ͕
    ҧ͏Մೳੑ͕͋Δ
    

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62. ͜ͷ໰୊ʹର͢ΔΞϓϩʔν
    αϒλΠϐϯάͷ࣮૷ํࣜ͸େ͖͘෼͚ͯ2ͭ
    1. inclusiveͳ࣮૷
    • ڞ௨ͷ࣮ߦ࣌ͷදݱΛ࢖͏
    • JavaͳͲ
    2.coerciveͳ࣮૷
    • ม׵ॲཧ(ܕڧ੍)ΛڬΈࠐΉ
    ← Swift͸ͬͪ͜
    

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63. ܕڧ੍ҙຯ࿦(coercion semantics)
    • ؆୯ʹݴ͏ͱɺ̍ͭͷαϒλΠϐϯάنଇʹ͍ͭͯɺ1
    ͭͷม׵ॲཧ(ܕڧ੍)͕ଘࡏ͢Δɻ
    • TypeChecker͸ɺͲͷαϒλΠϓؔ܎Λ࢖ͬͯܕνΣο
    ΫΛ௨͔ͨ͠Λه࿥͓͍ͯͯ͠ɺ͋ͱͰ࣮ࡍͷม׵ॲཧ
    Λૠೖ͢Δɻ
    • lib/Sema/CSApply.cppͷExprRewriterͱ͍͏Ϋϥε
    Λࢀߟɻ
    

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64. ྫ: Optionalͷ৔߹
    

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65. ྫ: Optionalͷ৔߹
    

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66. ྫ: Optionalͷ৔߹
    Constraint restrictions:
    Int to Optional is [value-to-optional]
    $ swift -frontend -typecheck -debug-constraints test.swift
    

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67. ྫ: Optionalͷ৔߹
    $ swiftc -dump-ast test.swift
    (inject_into_optional implicit type=‘Optional’ …
    (declref_expr type=‘Int' … ) )
    

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68. ྫ: Optionalͷ৔߹
    $ swiftc -emit-sil test.swift
    %9 = load %3 : $*Int
    %10 = enum $Optional, #Optional.some!enumelt.1, %9 : $Int
    store %10 to %8 : $*Optional
    %12 = integer_literal $Builtin.Int32, 0
    %13 = struct $Int32 (%12 : $Builtin.Int32)
    ͭ·ΓରԠ͢Δܕڧ੍͸ʮ.someͰแΉʯ
    

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69. Classͷ৔߹
    

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70. ྫ: Classͷ৔߹
    

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71. ྫ: Classͷ৔߹
    Constraint restrictions:
    Dog to Animal is [superclass]
    $ swift -frontend -typecheck -debug-constraints test.swift
    

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72. ྫ: Classͷ৔߹
    $ swiftc -dump-ast test.swift
    (derived_to_base_expr implicit type=‘Animal’ …
    (declref_expr type=‘Dog' … ) )
    

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73. ྫ: Classͷ৔߹
    $ swiftc -emit-sil test.swift
    …
    %10 = load %3 : $*Dog
    strong_retain %10 : $Dog
    %12 = upcast %10 : $Dog to $Animal
    store %12 to %9 : $*Animal
    %14 = integer_literal $Builtin.Int32, 0
    %15 = struct $Int32 (%14 : $Builtin.Int32)
    ͭ·ΓରԠ͢Δܕڧ੍͸ʮΞοϓΩϟετʯ
    

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74. ྫ:Existentialͷ৔߹
    աఔ͸লུ
    (erasure_expr implicit type=‘Animal’ …
    (declref_expr type=‘Dog' … ) )
    ରԠ͢Δܕڧ੍͸ʮଘࡏܕ΁ͷύοέʔδԽʯ
    ( = type erase)
    

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75. Swiftʹ͓͚Δʮ҉໧ม׵ʯ
    • Α͘ʮ҉໧ม׵ʯͳͲͱݺ͹ΕΔΞϨͷਖ਼ମ
    ͸΄΅΄΅αϒλΠϓؔ܎ʹج͍ͮͨܕڧ੍
    • ҉໧ม׵͋Δͱ͜ΖʹαϒλΠϐϯά͋Γ
    

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76. ࣮૷Λগ͚ͩ͠ݟΔ
    

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77. αϒλΠϐϯάʙܕڧ੍
    • ConstraintSystemͷConstraintRestrictionsʹ
    ࢖ͬͨαϒλΠϓؔ܎౳͕ه࿥͞ΕΔ
    • ExprRewriter::coerceToTypeͰܕڧ੍
    

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78. ExprRewriter::coerceToType
    ܕڧ੍(coercion)ͷॲཧΛ͍ͯ͠Δؔ਺
    

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79. ExprRewriter::coerceToType
    ConversionRestrictionKindʹԠͨ͡ॲཧ
    ͨͱ͑͹ValueToOptionalͳΒInjectIntoOptionalͱ͍͏
    ܕڧ੍Λૠೖ
    

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80. αϒλΠϐϯά·ͱΊ
    • αϒλΠϐϯά͸نଇʹΑͬͯఆٛ͞Ε͍ͯΔ
    • ͦΕͧΕنଇʹରԠ͢Δܕڧ੍͕ଘࡏ͢Δ
    • TypeChecker/ConstraintSystem͸ɺͲͷαϒ
    λΠϓؔ܎Λ࢖ͬͯܕνΣοΫΛ௨͔ͨ͠Λ֮
    ͓͍͑ͯͯɺ͋ͱͰ࣮ࡍͷม׵ॲཧΛૠೖ͢Δɻ
    

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81. ͓ΘΓ
    

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