[SE-0345] Support `if let foo {` optional binding conditions #40694

calda · 2021-12-22T22:21:03Z

This PR adds support for if let foo { optional binding conditions.

This implements SE-0345.

For example:

var foo: String? = "hello world"

if let foo {
  // `foo` is unwrapped to `String`
  print(foo) // prints "hello world"
}

DougGregor · 2022-01-04T17:16:54Z

@swift-ci please smoke test

DougGregor · 2022-01-04T17:17:02Z

@swift-ci please built toolchain

DougGregor · 2022-01-04T17:19:49Z

Could you add some tests into, e.g., test/stmt/if_while_var.swift, to show that this is doing the right thing in both well-formed cases (the x in if x { ... } is available and optional) and ill-formed cases (x doesn't exist, x isn't optional, etc.`)?

calda · 2022-01-04T17:22:26Z

Of course, will work on this tonight / this week. Thanks for the pointer of what tests to update!

calda · 2022-01-04T20:07:58Z

@DougGregor, added tests in 38e2b70

DougGregor · 2022-03-11T23:50:52Z

@swift-ci please build toolchain

DougGregor · 2022-03-15T20:40:43Z

@swift-ci please build toolchain

DougGregor · 2022-03-17T20:05:46Z

@swift-ci please smoke test

lib/Parse/ParseStmt.cpp

AnthonyLatsis · 2022-03-23T09:27:06Z

Could you also add some tests for the following?

if let x {} where x is not defined.
if let x: Int {} at least for a matching wrapped type.
if case let .y(x) {}, if case .y(let x) {}, if case let x?.

calda · 2022-03-24T00:43:41Z

Updated in cc85edf

DougGregor · 2022-03-31T04:20:54Z

@swift-ci please smoke test

DougGregor · 2022-03-31T04:22:06Z

SE-0345 has been accepted. Kicking off CI to check that we're in a mergeable state. One thing we'll still want to add is a ChangeLog entry describing the change. That can come as a separate PR, of course

calda · 2022-03-31T17:57:17Z

Woohoo! Thanks for merging @DougGregor, appreciate your leadership as RM throughout the review 😄

The issue is that the shorthand if let syntax injects an implicit expression: swiftlang#40694 in ParseStmt and that the 'diagnoseUnhandledAsyncSite' explicitly avoids reporting errors in implicit expressions. This patch "peeks" at the expression to notice this case, however perhaps we should mark this implicit expression in ParseStmt and then detect it explicitly. Added some tests covering this as well as properly erroring out for the nonexistent syntax of shortand + awaiting which doesn't exist, and we properly error on it. Resolves rdar://126169564

The issue is that the shorthand if let syntax injects an implicit expression: swiftlang#40694 in ParseStmt and that the 'diagnoseUnhandledAsyncSite' explicitly avoids reporting errors in implicit expressions. Since the synthesized node does have proper source location, we can avoid this problem easily if we dont mark it as Implicit. Other approaches are possible but end up in a whack-a-mole between a lot of other error reporting in other situations which do rely on implicit code not being reported because they report on it already in some other specialized way. Resolves rdar://126169564 what if we always diagnose Propsing we use this shape of fix for the async if let in synchronous code This change is that we don't mark the implicit declref code emitted by the `if let prop` as implicit anymore, and this way the reporting works out as expected. Removing the if (isImplicit) return-early is actually tricky since there's quite a whack-a-mole with errors getting reported then... This change looks the safest to me.

The issue is that the shorthand if let syntax injects an implicit expression: swiftlang#40694 in ParseStmt and that the 'diagnoseUnhandledAsyncSite' explicitly avoids reporting errors in implicit expressions. Since the synthesized node does have proper source location, we can avoid this problem easily if we dont mark it as Implicit. Other approaches are possible but end up in a whack-a-mole between a lot of other error reporting in other situations which do rely on implicit code not being reported because they report on it already in some other specialized way. Resolves rdar://126169564

The issue is that the shorthand if let syntax injects an implicit expression: swiftlang#40694 in ParseStmt and that the 'diagnoseUnhandledAsyncSite' explicitly avoids reporting errors in implicit expressions. This change is that we don't mark the implicit declref code emitted by the `if let prop` as implicit anymore, and this way the reporting works out as expected. Added some tests covering this as well as properly erroring out for the nonexistent syntax of shortand + awaiting which doesn't exist, and we properly error on it. Resolves rdar://126169564

The issue is that the shorthand if let syntax injects an implicit expression: apple#40694 in ParseStmt and that the 'diagnoseUnhandledAsyncSite' explicitly avoids reporting errors in implicit expressions. This change is that we don't mark the implicit declref code emitted by the `if let prop` as implicit anymore, and this way the reporting works out as expected. Added some tests covering this as well as properly erroring out for the nonexistent syntax of shortand + awaiting which doesn't exist, and we properly error on it. Resolves rdar://126169564

calda mentioned this pull request Dec 22, 2021

Add proposal for if let shorthand swiftlang/swift-evolution#1504

Merged

Implement support for 'if let foo {' syntax

b9c2370

calda force-pushed the cal--if-let-shorthand branch from ee8ebc0 to b9c2370 Compare January 4, 2022 17:36

calda force-pushed the cal--if-let-shorthand branch 3 times, most recently from 6cd6002 to 362234d Compare January 5, 2022 05:39

Add tests

38e2b70

calda force-pushed the cal--if-let-shorthand branch from 362234d to 38e2b70 Compare January 5, 2022 14:25

Improve diagnostic in cases like 'if let foo.bar'

ac7529f

Fix test failures

14076df

AnthonyLatsis reviewed Mar 23, 2022

View reviewed changes

lib/Parse/ParseStmt.cpp Outdated Show resolved Hide resolved

lib/Parse/ParseStmt.cpp Outdated Show resolved Hide resolved

Clean up implementation, add more tests

cc85edf

calda changed the title ~~Support if let foo { optional binding conditions~~ [SE-0345] Support if let foo { optional binding conditions Mar 31, 2022

DougGregor merged commit a6bcd80 into swiftlang:main Mar 31, 2022

calda mentioned this pull request Mar 31, 2022

Mark SE-0345 as implemented in Swift 5.7 swiftlang/swift-evolution#1594

Merged

ktoso mentioned this pull request Jun 17, 2024

[Concurrency] if let value on async value should be banned (not crash) #74475

Merged

ktoso mentioned this pull request Jun 18, 2024

[6.0][Concurrency] if let value on async value should be banned (not crash) #74514

Merged

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[SE-0345] Support `if let foo {` optional binding conditions #40694

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