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Array expression trailing closures #3223

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17 changes: 13 additions & 4 deletions Sources/SwiftParser/Expressions.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -932,10 +932,19 @@ extension Parser {
leadingExpr: RawExprSyntax,
flavor: ExprFlavor
) -> RawExprSyntax? {
guard
self.at(.leftBrace) && !leadingExpr.raw.kind.isLiteral
&& self.withLookahead({ $0.atValidTrailingClosure(flavor: flavor) })
else {
guard self.at(.leftBrace) else {
return nil
}

if leadingExpr.raw.kind.isLiteral {
// Trailing closures are allowed after array and dictionary types,
// since this can mean `[Element].init { }` or `[Key: Value].init { }`.
guard leadingExpr.raw.kind == .arrayExpr || leadingExpr.raw.kind == .dictionaryExpr else {
return nil
}
}

guard self.withLookahead({ $0.atValidTrailingClosure(flavor: flavor) }) else {
return nil
}

Expand Down
92 changes: 76 additions & 16 deletions Tests/SwiftParserTest/ExpressionTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,80 @@ final class ExpressionTests: ParserTestCase {
assertParse("compactMap { (parserDiag) in }")
}

func testCollectionTrailingClosureInits() {
assertParse(
"let value = 1️⃣[Foo] { bar }",
substructure: FunctionCallExprSyntax(
calledExpression: ArrayExprSyntax(
leftSquare: .leftSquareToken(),
elements: ArrayElementListSyntax([
ArrayElementSyntax(
expression: DeclReferenceExprSyntax(baseName: .identifier("Foo")),
trailingComma: nil
)
]),
rightSquare: .rightSquareToken()
),
leftParen: nil,
arguments: LabeledExprListSyntax([]),
rightParen: nil,
trailingClosure: ClosureExprSyntax(
leftBrace: .leftBraceToken(),
signature: nil,
statements: CodeBlockItemListSyntax([
CodeBlockItemSyntax(
item: .expr(
ExprSyntax(
DeclReferenceExprSyntax(baseName: .identifier("bar"))
)
)
)
]),
rightBrace: .rightBraceToken()
)
),
substructureAfterMarker: "1️⃣"
)

assertParse(
"let value = 1️⃣[String: Int] { value }",
substructure: FunctionCallExprSyntax(
calledExpression: DictionaryExprSyntax(
leftSquare: .leftSquareToken(),
content: .elements(
DictionaryElementListSyntax([
DictionaryElementSyntax(
key: DeclReferenceExprSyntax(baseName: .identifier("String")),
colon: .colonToken(),
value: DeclReferenceExprSyntax(baseName: .identifier("Int")),
trailingComma: nil
)
])
),
rightSquare: .rightSquareToken()
),
leftParen: nil,
arguments: LabeledExprListSyntax([]),
rightParen: nil,
trailingClosure: ClosureExprSyntax(
leftBrace: .leftBraceToken(),
signature: nil,
statements: CodeBlockItemListSyntax([
CodeBlockItemSyntax(
item: .expr(
ExprSyntax(
DeclReferenceExprSyntax(baseName: .identifier("value"))
)
)
)
]),
rightBrace: .rightBraceToken()
)
),
substructureAfterMarker: "1️⃣"
)
}

func testSequenceExpressions() {
assertParse("await a()")
assertParse(
Expand Down Expand Up @@ -2180,22 +2254,8 @@ final class ExpressionTests: ParserTestCase {
{ return /foo/ }
"""
)
assertParse(
"_ = [1]1️⃣ { return [1] }",
diagnostics: expectedDiagnostics,
fixedSource: """
_ = [1]
{ return [1] }
"""
)
assertParse(
"_ = [1: 1]1️⃣ { return [1: 1] }",
diagnostics: expectedDiagnostics,
fixedSource: """
_ = [1: 1]
{ return [1: 1] }
"""
)
assertParse("_ = [1] { return [1] }")
assertParse("_ = [1: 1] { return [1: 1] }")
Comment on lines +2257 to +2258
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@calda calda Dec 31, 2025

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These now parse, but fail type checking in the full compiler:

  _ = [1] { return [1] } // expected-error {{cannot call value of non-function type '[Int]'}}
  _ = [1: 1] { return [1: 1] } // expected-error {{cannot call value of non-function type '[Int : Int]'}}

  _ = [1] // expected-error {{cannot call value of non-function type '[Int]'}}
  { return [1] }

  _ = [1: 1] // expected-error {{cannot call value of non-function type '[Int : Int]'}}
  { return [1: 1] }


assertParse(
"_ = 1 + 11️⃣ { return 1 }",
Expand Down