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Multi-statement closure type inference #32223

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Multi-statement closure type inference #32223

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DougGregor
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@DougGregor DougGregor commented Jun 6, 2020 •
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Introduce support for type inference of closures with multiple
statements. Type inference flows from the closure parameters through
the body of the closure to determine the return type. This, for example,
allows a "map" closure with multiple statements to infer the result type
based on the "return" in the body:

let _ = ints.map { i in
  let value = i + 1
  return String(value)
}

The frontend option -experimental-multi-statement-closures enables
this new behavior. It should cover all statement and declaration kinds
in a closure now:

  • Expressions
  • Brace statements
  • var/let declarations (note: only when there is also an initializer)
  • do statements (without a catch)
  • do statements (with catch clauses)
  • if statements
  • guard statements
  • while loops
  • repeat-while loops
  • for..in loops
  • throw statements
  • defer statements
  • break and continue
  • switch statements
  • #assert statements
  • Other kinds of declarations (local types, etc.)

@DougGregor DougGregor marked this pull request as draft June 6, 2020 05:59
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@swift-ci please smoke test

@DougGregor DougGregor force-pushed the multi-statement-closures branch from 17b0fcd to 49b37f9 Compare June 7, 2020 05:02
@DougGregor
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@swift-ci smoke test

@DougGregor
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@swift-ci smoke test macOS

@MaxDesiatov MaxDesiatov mentioned this pull request Jun 9, 2020
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@shadaj shadaj mentioned this pull request Jun 11, 2020
Closed
8 tasks
@DougGregor DougGregor force-pushed the multi-statement-closures branch from 49b37f9 to 68a6ff1 Compare August 6, 2020 05:34
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@swift-ci please smoke test

@fabianfett fabianfett mentioned this pull request Aug 10, 2020
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@DougGregor
Add experimental support for multi-statement closure inference.
3631ddb 
Introduce support for type inference of closures with multiple
statements. Type inference flows from the closure parameters through
the body of the closure to determine the return type. This, for example,
allows a "map" closure with multiple statements to infer the result type
based on the "return" in the body:

    let _ = ints.map { i in
      print(i)
      return String(i)
    }

The frontend option `-experimental-multi-statement-closures` enables
this new behavior. Only simple expression statements in closures work
thus far.
@DougGregor
[Multi-statement closures] Add support for pattern bindings (let/var …
692b8aa 
…decls).
@DougGregor
[Multi-statement closures] Add support for "do" statements.
99c29f6
@DougGregor
[Multi-statement closures] Add support for "if" statements.
2d74c55
@DougGregor
[Multi-statement closures] Add support for "guard" statements.
3f14a42
@DougGregor
[Multi-statement closures] Add support for "while" loops.
1ea05d2
@DougGregor
[Constraint system] Extend SolutionApplicationTargetKey for expressions.
39c2232
@DougGregor
[Multi-statement closures] Consistently record expression targets.
720133b
@DougGregor
[Multi-statement closures] Add support for repeat-while loops.
6d57439
@DougGregor
[Multi-expression closures] Add support for for..in loops.
0198a70
@DougGregor
[Multi-expression closures] Add support for break & continue statements.
1ee7672
@DougGregor
[Multi-expression closures] Add support for 'defer' statement.
0d5987d
@DougGregor
[Multi-expression closures] Add support for 'throw' statement.
0dae0bb
@DougGregor
[Multi-expression closures] Add support for experimental #assert stat…
5c16778 
…ement
@DougGregor
[Multi-expression closures] Add support for 'switch' and 'fallthrough…
7a655e3 
…' statements.
@DougGregor
[Multi-expression closures] Add support for do-catch statements.
594b635
@DougGregor
[Multi-expression closures] Add support for remaining declarations
9e22826
@DougGregor DougGregor force-pushed the multi-statement-closures branch from 5f73625 to 9e22826 Compare August 15, 2020 05:57
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@swift-ci smoke test

@shahmishal
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Please update the base branch to main by Oct 5th otherwise the pull request will be closed automatically.

  • How to change the base branch: (Link)
  • More detail about the branch update: (Link)

@shahmishal shahmishal closed this Oct 5, 2020
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xwu commented Oct 5, 2020

Darn, was really pumped about this. Any chance it’ll be resurrected?

@IanKeen
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IanKeen commented May 18, 2021

same, I hope this makes a comeback! :(

@xedin xedin mentioned this pull request Oct 6, 2021
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4 participants
@DougGregor @shahmishal @xwu @IanKeen