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[SwiftParser] Experimental feature flags for _borrow and _move #3018

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Merged
merged 1 commit into from
Mar 17, 2025
Merged

[SwiftParser] Experimental feature flags for _borrow and _move #3018

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5 changes: 5 additions & 0 deletions CodeGeneration/Sources/SyntaxSupport/ExperimentalFeatures.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ public enum ExperimentalFeature: String, CaseIterable {
case valueGenerics
case abiAttribute
case keypathWithMethodMembers
case oldOwnershipOperatorSpellings

/// The name of the feature as it is written in the compiler's `Features.def` file.
public var featureName: String {
Expand All @@ -44,6 +45,8 @@ public enum ExperimentalFeature: String, CaseIterable {
return "ABIAttribute"
case .keypathWithMethodMembers:
return "KeypathWithMethodMembers"
case .oldOwnershipOperatorSpellings:
return "OldOwnershipOperatorSpellings"
}
}

Expand All @@ -68,6 +71,8 @@ public enum ExperimentalFeature: String, CaseIterable {
return "@abi attribute"
case .keypathWithMethodMembers:
return "keypaths with method members"
case .oldOwnershipOperatorSpellings:
return "`_move` and `_borrow` as ownership operators"
}
}

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18 changes: 5 additions & 13 deletions Sources/SwiftParser/Expressions.swift
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Expand Up @@ -481,20 +481,9 @@ extension Parser {
arena: self.arena
)
)
case (._move, let handle)?:
let moveKeyword = self.eat(handle)
let sub = self.parseSequenceExpressionElement(
flavor: flavor,
pattern: pattern
)
return RawExprSyntax(
RawConsumeExprSyntax(
consumeKeyword: moveKeyword,
expression: sub,
arena: self.arena
)
)

case (._borrow, let handle)?:
assert(self.experimentalFeatures.contains(.oldOwnershipOperatorSpellings))
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Could you make these preconditions?

swift-syntax/Sources/SwiftSyntax/Assert.swift

Lines 13 to 22 in ee01462

/// How to choose `assert` vs. `precondition`:
/// - Wherever possible, it is preferable to emit a diagnostic instead of
/// using `precondition`. This way the parser won't crash if the condition is
/// violated.
/// - If you think the diagnostic added above should never be emitted, it is
/// fine to also emit an `assertionFailure` in debug builds to make it easier
/// to debug the unexpected diagnostic.
/// - If in doubt always use `precondition`
/// - `assert` should only be used if checking the assertion has a non-trivial
/// cost and provides little benefit in terms of safety in release builds.

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I'm not really sure it worth, although it trivial, The branch is a result of the subject expression, where the experimentalFeatures is handled, which is close enough for not checking seriously. Also even if somehow we enter this branch without oldOwnershipOperatorSpellings feature in release builds, we still have atContextualExpressionModifier() condtion check below so the check is just to make sure the condition check in ExpressionModifierKeyword.init(lexeme:) is working.

FWIW, looking at the existing code, do expression uses precodition but then statement uses assert.

fallthrough
case (.borrow, let handle)?:
if !atContextualExpressionModifier() {
Expand Down Expand Up @@ -531,6 +520,9 @@ extension Parser {
)
)

case (._move, let handle)?:
assert(self.experimentalFeatures.contains(.oldOwnershipOperatorSpellings))
fallthrough
case (.consume, let handle)?:
if !atContextualExpressionModifier() {
break EXPR_PREFIX
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4 changes: 2 additions & 2 deletions Sources/SwiftParser/TokenSpecSet.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -705,8 +705,8 @@ enum ExpressionModifierKeyword: TokenSpecSet {
init?(lexeme: Lexer.Lexeme, experimentalFeatures: Parser.ExperimentalFeatures) {
switch PrepareForKeywordMatch(lexeme) {
case TokenSpec(.await): self = .await
case TokenSpec(._move): self = ._move
case TokenSpec(._borrow): self = ._borrow
case TokenSpec(._move) where experimentalFeatures.contains(.oldOwnershipOperatorSpellings): self = ._move
case TokenSpec(._borrow) where experimentalFeatures.contains(.oldOwnershipOperatorSpellings): self = ._borrow
case TokenSpec(.try): self = .try
case TokenSpec(.borrow): self = .borrow
case TokenSpec(.consume): self = .consume
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5 changes: 5 additions & 0 deletions Sources/SwiftParser/generated/ExperimentalFeatures.swift
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18 changes: 9 additions & 9 deletions Tests/SwiftParserTest/ExpressionTests.swift
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Expand Up @@ -1557,18 +1557,18 @@ final class ExpressionTests: ParserTestCase {
)
}

func testMoveExpression() {
assertParse("_move msg")
assertParse("use(_move msg)")
assertParse("_move msg")
assertParse("let b = (_move self).buffer")
func testConsumeExpression() {
assertParse("consume msg")
assertParse("use(consume msg)")
assertParse("consume msg")
assertParse("let b = (consume self).buffer")
}

func testBorrowExpression() {
assertParse("_borrow msg")
assertParse("use(_borrow msg)")
assertParse("_borrow msg")
assertParse("let b = (_borrow self).buffer")
assertParse("borrow msg")
assertParse("use(borrow msg)")
assertParse("borrow msg")
assertParse("let b = (borrow self).buffer")
assertParse("borrow msg")
assertParse("use(borrow msg)")
assertParse("borrow(msg)")
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8 changes: 6 additions & 2 deletions Tests/SwiftParserTest/translated/BorrowExprTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,8 @@

// This test file has been translated from swift/test/Parse/borrow_expr.swift

@_spi(ExperimentalLanguageFeatures) import SwiftParser
import SwiftSyntax
import XCTest

final class BorrowExprTests: ParserTestCase {
Expand All @@ -23,7 +25,8 @@ final class BorrowExprTests: ParserTestCase {
func testGlobal() {
useString(_borrow global)
}
"""
""",
experimentalFeatures: [.oldOwnershipOperatorSpellings]
)
}

Expand All @@ -36,7 +39,8 @@ final class BorrowExprTests: ParserTestCase {
t = String()
useString(_borrow t)
}
"""
""",
experimentalFeatures: [.oldOwnershipOperatorSpellings]
)
}

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60 changes: 58 additions & 2 deletions Tests/SwiftParserTest/translated/MoveExprTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,8 @@

// This test file has been translated from swift/test/Parse/move_expr.swift

@_spi(ExperimentalLanguageFeatures) import SwiftParser
import SwiftSyntax
import XCTest

final class MoveExprTests: ParserTestCase {
Expand All @@ -22,7 +24,8 @@ final class MoveExprTests: ParserTestCase {
func testGlobal() {
let _ = _move global
}
"""
""",
experimentalFeatures: [.oldOwnershipOperatorSpellings]
)
}

Expand All @@ -33,7 +36,9 @@ final class MoveExprTests: ParserTestCase {
let t = String()
let _ = _move t
}
"""
""",
experimentalFeatures: [.oldOwnershipOperatorSpellings]

)
}

Expand All @@ -45,7 +50,58 @@ final class MoveExprTests: ParserTestCase {
t = String()
let _ = _move t
}
""",
experimentalFeatures: [.oldOwnershipOperatorSpellings]
)
}

func testMoveExpr4() {
assertParse(
"""
_move(t)
""",
substructure: FunctionCallExprSyntax(
calledExpression: DeclReferenceExprSyntax(baseName: .identifier("_move")),
leftParen: .leftParenToken(),
arguments: [.init(expression: DeclReferenceExprSyntax(baseName: .identifier("t")))],
rightParen: .rightParenToken()
),
experimentalFeatures: [.oldOwnershipOperatorSpellings]
)
}

func testMoveExpr5() {
assertParse(
"""
_move(t)
""",
substructure: FunctionCallExprSyntax(
calledExpression: DeclReferenceExprSyntax(baseName: .identifier("_move")),
leftParen: .leftParenToken(),
arguments: [.init(expression: DeclReferenceExprSyntax(baseName: .identifier("t")))],
rightParen: .rightParenToken()
),
experimentalFeatures: []
)
}

func testMoveExpr6() {
assertParse(
"""
_move1️⃣ t
""",
diagnostics: [
DiagnosticSpec(
message: "consecutive statements on a line must be separated by newline or ';'",
fixIts: ["insert newline", "insert ';'"]
)
],
fixedSource:
"""
_move
t
""",
experimentalFeatures: []
)
}

Expand Down