COMPLETE MONITORS FOR GRADUAL TYPES Ben Greenman Matthias - PowerPoint PPT Presentation

Ben Greenman Matthias Felleisen Christos Dimoulas at at at COMPLETE MONITORS FOR GRADUAL TYPES

Ben Greenman Matthias Felleisen Christos Dimoulas at at at COMPLETE MONITORS FOR GRADUAL TYPES a careful analysis of the mixed-typed design space

Type soundness is not enough Complete monitoring is crucial for meaningful gradual types "Incomplete" monitoring provides a way to measure the quality of blame errors *from ESOP 2012 *

Mixed-Typed Language

Untyped/Typed mix Mixed-Typed Language = untyped code = simply-typed (no 'Dynamic' type) code U U U T T T U

A Few Motivations U U T T U

Prototyping A Few Motivations U U T T U

Prototyping A Few Motivations write untyped code, rely on types U U T T U

Prototyping A Few Motivations write untyped code, rely on types Re-Use U U T T U

Prototyping A Few Motivations write untyped code, rely on types Re-Use write typed code, use old libraries U U T T U

Many Implementations ... Python TypeScript JavaScript + Hack PHP + Mypy + JavaScript Reticulated Python + Typed Racket Racket + Flow +

Many Implementations ... JavaScript ... diffcult to compare + TypeScript JavaScript + Hack PHP + Mypy Python + Reticulated Python + Typed Racket Racket + Flow UTU U T

Many Models, too GTLC AGT λH λ* → UTU U T

Goal: Characterize the Landscape

Non-Goal : Restrict Landscape

Warmup: Optional Typing / Erasure

Example: Optional Typing T function f (x : [N,N]) { ... fst x ... }

Example: Optional Typing T U function f (x : [N,N]) { f(9) ... fst x ... }

Example: Optional Typing T U function f (x : [N,N]) { f(9) ... fst x ... } Error: 9 is not a pair

types are meaningless at run-time Example: Optional Typing cannot help debug a faulty program T U function f (x : [N,N]) { f(9) ... fst x ... } Error: 9 is not a pair

= Does Not Preserve Types Uni sound

= Does Not Preserve Types Uni sound "type" sound

ICFP '18

ICFP '18 : Three Semantics, Soundnesses

ICFP '18 : Three Semantics, Soundnesses Erasure semantics - types predict nothing

ICFP '18 : Three Semantics, Soundnesses Erasure semantics - types predict nothing Transient semantics - types predict the top-level shape of values - enforced by tag checks

ICFP '18 : Three Semantics, Soundnesses Erasure semantics - types predict nothing Transient semantics - types predict the top-level shape of values - enforced by tag checks Natural semantics - types predict the full behavior of values - enforced by higher-order wrappers

ICFP '18 : Three Semantics, Soundnesses T sound - types predict the full behavior of values Natural semantics - enforced by tag checks - types predict the top-level shape of values Transient semantics - types predict nothing Erasure semantics - enforced by higher-order wrappers Erasure semantics Uni sound - enforced by higher-order wrappers - types predict the full behavior of values Natural semantics - enforced by tag checks - types predict the top-level shape of values Transient semantics - types predict nothing ⌊ T ⌋ sound

ICFP '18: A Spectrum of Type Soundness Uni sound

ICFP '18: A Spectrum of Type Soundness Uni sound Uni sound T sound Erasure Natural Transient ⌊ T ⌋ sound

Natural T sound Transient ⌊ T ⌋ sound

- enforced by higher-order wrappers T sound - types predict the full behavior of values Natural semantics - enforced by tag checks - types predict the top-level shape of values Transient semantics T sound - enforced by higher-order wrappers - types predict the full behavior of values Natural semantics - enforced by tag checks - types predict the top-level shape of values Transient semantics Transient Natural ⌊ T ⌋ sound ⌊ T ⌋ sound

Natural T sound Transient ⌊ T ⌋ sound

T sound Natural Transient Amnesic Amnesic semantics with higher-order wrappers - same behavior as Transient - same type soundness as Natural OOPSLA '19 Greenberg POPL '15 Castagna, Lanvin ICFP '17 ⌊ T ⌋ sound - enforce tag checks ⌊ T ⌋

Type Soundness is NOT ENOUGH Uni sound T sound ??? Erasure Natural Transient Amnesic ⌊ T ⌋ sound

Example: Transient/Amnesic vs. Natural

Example: Transient/Amnesic vs. Natural Prototyping

Example: Transient/Amnesic vs. Natural Prototyping Library Re-Use

Example: Transient/Amnesic vs. Natural Prototyping Library Re-Use Combine: untyped script + typed API + untyped library via a higher-order value

Example: Transient/Amnesic vs. Natural 1. plot data 2. listen for a click 3. draw an image Clickable Plot 1

Example: Transient/Amnesic vs. Natural 1. plot data 2. listen for a click 3. draw an image Clickable Plot 2

Example: Transient/Amnesic vs. Natural 1. plot data 2. listen for a click 3. draw an image Clickable Plot 3

Example: interactive plot Client Library API U T U

Example: interactive plot Client API Library U T U function h(x) { if (0 < fst x): pumpkin else : fish } p = ClickPlot(h) p.show() // click

Example: interactive plot Client API Library U T U function h(x) { class ClickPlot { if (0 < fst x): constructor ( pumpkin onClick){...} else : fish mouseHandler(evt){ } i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show(){...} // click }

Example: interactive plot Library Client API U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Library Client API U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Library Client API Promises a pair of numbers U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Library Client API Promises a pair of numbers U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Library Promises a pair of numbers Client API Expects a pair of numbers U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Library Client API U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Library Client API U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Client Library API U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i Sends MouseEvt value p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }

Example: interactive plot Client Library API U T U function h(x) { type ClickPlot { class ClickPlot { if (0 < fst x): constructor ( constructor ( pumpkin ([N,N]) => Image) onClick){...} else : [N,N] != MouseEvt fish mouseHandler : mouseHandler(evt){ } (MouseEvt) => Void i = onClick(evt) // draw i Sends MouseEvt value p = ClickPlot(h) } p.show() show : () => Void show(){...} // click } }