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Merged
merged 1 commit into from
Jul 25, 2023
Merged

Introduce peek(isAt:) #1942

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2 changes: 1 addition & 1 deletion Sources/SwiftParser/Availability.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,7 @@ extension Parser {
case (.star, _)?:
entry = self.parseAvailabilitySpec()
case (.identifier, let handle)?:
if self.peek().rawTokenKind == .comma {
if self.peek(isAt: .comma) {
// An argument like `_iOS13Aligned` that isn't followed by a version.
let version = self.eat(handle)
entry = .token(version)
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8 changes: 4 additions & 4 deletions Sources/SwiftParser/Declarations.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -252,8 +252,8 @@ extension Parser {
return RawDeclSyntax(self.parseMacroExpansionDeclaration(attrs, handle))
case nil:
if inMemberDeclList {
let isProbablyVarDecl = self.at(.identifier, .wildcard) && self.peek().rawTokenKind.is(.colon, .equal, .comma)
let isProbablyTupleDecl = self.at(.leftParen) && self.peek().rawTokenKind.is(.identifier, .wildcard)
let isProbablyVarDecl = self.at(.identifier, .wildcard) && self.peek(isAt: .colon, .equal, .comma)
let isProbablyTupleDecl = self.at(.leftParen) && self.peek(isAt: .identifier, .wildcard)

if isProbablyVarDecl || isProbablyTupleDecl {
return RawDeclSyntax(self.parseBindingDeclaration(attrs, .missing(.keyword(.var))))
Expand Down Expand Up @@ -1036,7 +1036,7 @@ extension Parser {
let identifier: RawTokenSyntax
if self.at(anyIn: Operator.self) != nil || self.at(.exclamationMark, .prefixAmpersand) {
var name = self.currentToken.tokenText
if name.count > 1 && name.hasSuffix("<") && self.peek().rawTokenKind == .identifier {
if name.count > 1 && name.hasSuffix("<") && self.peek(isAt: .identifier) {
name = SyntaxText(rebasing: name.dropLast())
}
unexpectedBeforeIdentifier = nil
Expand Down Expand Up @@ -1121,7 +1121,7 @@ extension Parser {
let (unexpectedBeforeSubscriptKeyword, subscriptKeyword) = self.eat(handle)

let unexpectedName: RawTokenSyntax?
if self.at(.identifier) && self.peek().tokenText.hasPrefix("<") || self.peek().rawTokenKind == .leftParen {
if self.at(.identifier) && self.peek().tokenText.hasPrefix("<") || self.peek(isAt: .leftParen) {
unexpectedName = self.consumeAnyToken()
} else {
unexpectedName = nil
Expand Down
67 changes: 24 additions & 43 deletions Sources/SwiftParser/Expressions.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -320,7 +320,7 @@ extension Parser {
return parseUnresolvedAsExpr(handle: handle)

case (.async, _)?:
if self.peek().rawTokenKind == .arrow || TokenSpec(.throws) ~= self.peek() {
if self.peek(isAt: .arrow, .keyword(.throws)) {
fallthrough
} else {
return nil
Expand Down Expand Up @@ -348,6 +348,20 @@ extension Parser {
}
}

/// Whether the current token is a valid contextual exprssion modifier like
/// `copy`, `consume`.
///
/// `copy` etc. are only contextually a keyword if they are followed by an
/// identifier or keyword on the same line. We do this to ensure that we do
/// not break any copy functions defined by users.
private mutating func isContextualExpressionModifier() -> Bool {
return self.peek(
isAt: TokenSpec(.identifier, allowAtStartOfLine: false),
TokenSpec(.dollarIdentifier, allowAtStartOfLine: false),
TokenSpec(.self, allowAtStartOfLine: false)
)
}

/// Parse an expression sequence element.
mutating func parseSequenceExpressionElement(
_ flavor: ExprFlavor,
Expand Down Expand Up @@ -430,17 +444,7 @@ extension Parser {
)

case (.copy, let handle)?:
// `copy` is only contextually a keyword, if it's followed by an
// identifier or keyword on the same line. We do this to ensure that we do
// not break any copy functions defined by users. This is following with
// what we have done for the consume keyword.
switch self.peek() {
case TokenSpec(.identifier, allowAtStartOfLine: false),
TokenSpec(.dollarIdentifier, allowAtStartOfLine: false),
TokenSpec(.self, allowAtStartOfLine: false):
break
default:
// Break out of `outer switch` on failure.
if !isContextualExpressionModifier() {
break EXPR_PREFIX
}

Expand All @@ -459,17 +463,7 @@ extension Parser {
)

case (.consume, let handle)?:
// `consume` is only contextually a keyword, if it's followed by an
// identifier or keyword on the same line. We do this to ensure that we do
// not break any copy functions defined by users. This is following with
// what we have done for the consume keyword.
switch self.peek() {
case TokenSpec(.identifier, allowAtStartOfLine: false),
TokenSpec(.dollarIdentifier, allowAtStartOfLine: false),
TokenSpec(.self, allowAtStartOfLine: false):
break
default:
// Break out of the outer `switch`.
if !isContextualExpressionModifier() {
break EXPR_PREFIX
}

Expand All @@ -492,17 +486,7 @@ extension Parser {
return RawExprSyntax(parsePackExpansionExpr(repeatHandle: handle, flavor, pattern: pattern))

case (.each, let handle)?:
// `each` is only contextually a keyword, if it's followed by an
// identifier or 'self' on the same line. We do this to ensure that we do
// not break any 'each' functions defined by users. This is following with
// what we have done for the consume keyword.
switch self.peek() {
case TokenSpec(.identifier, allowAtStartOfLine: false),
TokenSpec(.dollarIdentifier, allowAtStartOfLine: false),
TokenSpec(.self, allowAtStartOfLine: false):
break
default:
// Break out of `outer switch` on failure.
if !isContextualExpressionModifier() {
break EXPR_PREFIX
}

Expand All @@ -517,11 +501,10 @@ extension Parser {
)

case (.any, _)?:
// `any` is only contextually a keyword if it's followed by an identifier
// on the same line.
guard case TokenSpec(.identifier, allowAtStartOfLine: false) = self.peek() else {
if !isContextualExpressionModifier() {
break EXPR_PREFIX
}

// 'any' is parsed as a part of 'type'.
let type = self.parseType()
return RawExprSyntax(RawTypeExprSyntax(type: type, arena: self.arena))
Expand Down Expand Up @@ -995,7 +978,7 @@ extension Parser {
// Check for a [] or .[] suffix. The latter is only permitted when there
// are no components.
if self.at(TokenSpec(.leftSquare, allowAtStartOfLine: false))
|| (components.isEmpty && self.at(.period) && self.peek().rawTokenKind == .leftSquare)
|| (components.isEmpty && self.at(.period) && self.peek(isAt: .leftSquare))
{
// Consume the '.', if it's allowed here.
let period: RawTokenSyntax?
Expand Down Expand Up @@ -1722,7 +1705,7 @@ extension Parser {
let unexpectedBeforeEqual: RawUnexpectedNodesSyntax?
let equal: RawTokenSyntax?
let expression: RawExprSyntax
if self.peek().rawTokenKind == .equal {
if self.peek(isAt: .equal) {
// The name is a new declaration.
(unexpectedBeforeName, name) = self.expect(.identifier, TokenSpec(.self, remapping: .identifier), default: .identifier)
(unexpectedBeforeEqual, equal) = self.expect(.equal)
Expand Down Expand Up @@ -1901,7 +1884,7 @@ extension Parser {
let unexpectedBeforeLabel: RawUnexpectedNodesSyntax?
let label: RawTokenSyntax?
let colon: RawTokenSyntax?
if self.atArgumentLabel(allowDollarIdentifier: true) && self.peek().rawTokenKind == .colon {
if self.atArgumentLabel(allowDollarIdentifier: true) && self.peek(isAt: .colon) {
(unexpectedBeforeLabel, label) = parseArgumentLabel()
colon = consumeAnyToken()
} else {
Expand All @@ -1914,9 +1897,7 @@ extension Parser {
// this case lexes as a binary operator because it neither leads nor
// follows a proper subexpression.
let expr: RawExprSyntax
if self.at(.binaryOperator)
&& (self.peek().rawTokenKind == .comma || self.peek().rawTokenKind == .rightParen || self.peek().rawTokenKind == .rightSquare)
{
if self.at(.binaryOperator) && self.peek(isAt: .comma, .rightParen, .rightSquare) {
let (ident, args) = self.parseDeclNameRef(.operators)
expr = RawExprSyntax(
RawIdentifierExprSyntax(
Expand Down
8 changes: 3 additions & 5 deletions Sources/SwiftParser/Names.swift
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Expand Up @@ -93,12 +93,10 @@ extension Parser {

// Okay, let's look ahead and see if the next token is something that could
// be in an arg label list...
let next = self.peek()

// A close parenthesis, if empty lists are allowed.
let nextIsRParen = flags.contains(.zeroArgCompoundNames) && next.rawTokenKind == .rightParen
let nextIsRParen = flags.contains(.zeroArgCompoundNames) && peek(isAt: .rightParen)
// An argument label.
let nextIsArgLabel = next.isArgumentLabel() || next.rawTokenKind == .colon
let nextIsArgLabel = peek().isArgumentLabel() || peek(isAt: .colon)

guard nextIsRParen || nextIsArgLabel else {
return nil
Expand All @@ -117,7 +115,7 @@ extension Parser {
var loopProgress = LoopProgressCondition()
while !self.at(.endOfFile, .rightParen) && self.hasProgressed(&loopProgress) {
// Check to see if there is an argument label.
precondition(self.atArgumentLabel() && self.peek().rawTokenKind == .colon)
precondition(self.atArgumentLabel() && self.peek(isAt: .colon))
let name = self.consumeAnyToken()
let (unexpectedBeforeColon, colon) = self.expect(.colon)
elements.append(
Expand Down
2 changes: 1 addition & 1 deletion Sources/SwiftParser/Patterns.swift
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Expand Up @@ -181,7 +181,7 @@ extension Parser {

/// If we have something like `x SomeType`, use the indication that `SomeType` starts with a capital letter (and is thus probably a type name)
/// as an indication that the user forgot to write the colon instead of forgetting to write the comma to separate two elements.
if label == nil, colon == nil, self.at(.identifier), peek().rawTokenKind == .identifier, peek().tokenText.isStartingWithUppercase {
if label == nil, colon == nil, self.at(.identifier), peek(isAt: .identifier), peek().tokenText.isStartingWithUppercase {
label = consume(if: .identifier)
colon = self.missingToken(.colon)
}
Expand Down
2 changes: 1 addition & 1 deletion Sources/SwiftParser/Statements.swift
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Expand Up @@ -177,7 +177,7 @@ extension Parser {
guard
self.at(.keyword(.let), .keyword(.var), .keyword(.case))
|| self.at(.keyword(.inout))
|| (lastBindingKind != nil && self.peek().rawTokenKind == .equal)
|| (lastBindingKind != nil && self.peek(isAt: .equal))
else {
// If we lack it, then this is theoretically a boolean condition.
// However, we also need to handle migrating from Swift 2 syntax, in
Expand Down
10 changes: 0 additions & 10 deletions Sources/SwiftParser/SyntaxUtils.swift
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Expand Up @@ -113,16 +113,6 @@ extension SyntaxText {
}
}

extension RawTokenKind {
func `is`(_ kind1: RawTokenKind, _ kind2: RawTokenKind) -> Bool {
return self == kind1 || self == kind2
}

func `is`(_ kind1: RawTokenKind, _ kind2: RawTokenKind, _ kind3: RawTokenKind) -> Bool {
return self == kind1 || self == kind2 || self == kind3
}
}

extension RawTriviaPiece {
var isIndentationWhitespace: Bool {
switch self {
Expand Down
51 changes: 51 additions & 0 deletions Sources/SwiftParser/TokenConsumer.swift
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Expand Up @@ -172,6 +172,57 @@ extension TokenConsumer {
}
}

extension TokenConsumer {
/// Returns whether the next (peeked) token matches `spec`
@inline(__always)
mutating func peek(isAt spec: TokenSpec) -> Bool {
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Thoughts on just at instead of isAt? next could work as well. Or maybe nextAt(_:) instead of peek to match at(_:)?

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I deliberately decided against peek(at:) because we already have peek(at offset: Int) in the lexer, which peeks offset bytes ahead, which has completely different semantics.

We could consider renaming peek to next altogether. I’m not sure how much of a term of art peek is in parsers in general and whether we should stick to it because of that reason though.

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Could also change peek(at offset: Int) to something else. You don't need to block the PR on this though, easy enough to rename peek(isAt:) if we want to after.

#if SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION
if shouldRecordAlternativeTokenChoices {
recordAlternativeTokenChoice(for: self.peek(), choices: [spec])
}
#endif
return spec ~= self.peek()
}

/// Returns whether the next (peeked) token matches one of the two specs.
@inline(__always)
mutating func peek(
isAt spec1: TokenSpec,
_ spec2: TokenSpec
) -> Bool {
#if SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION
if shouldRecordAlternativeTokenChoices {
recordAlternativeTokenChoice(for: self.peek(), choices: [spec1, spec2])
}
#endif
switch self.peek() {
case spec1: return true
case spec2: return true
default: return false
}
}

/// Returns whether the next (peeked) token matches one of the three specs.
@inline(__always)
mutating func peek(
isAt spec1: TokenSpec,
_ spec2: TokenSpec,
_ spec3: TokenSpec
) -> Bool {
#if SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION
if shouldRecordAlternativeTokenChoices {
recordAlternativeTokenChoice(for: self.peek(), choices: [spec1, spec2, spec3])
}
#endif
switch self.peek() {
case spec1: return true
case spec2: return true
case spec3: return true
default: return false
}
}
}

// MARK: Consuming tokens (`consume`)

extension TokenConsumer {
Expand Down
2 changes: 1 addition & 1 deletion Sources/SwiftParser/Types.swift
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Expand Up @@ -457,7 +457,7 @@ extension Parser {
second = nil
unexpectedBeforeColon = nil
colon = parsedColon
} else if self.atArgumentLabel(allowDollarIdentifier: true) && self.peek().rawTokenKind == .colon {
} else if self.atArgumentLabel(allowDollarIdentifier: true) && self.peek(isAt: .colon) {
(unexpectedBeforeSecond, second) = self.parseArgumentLabel()
(unexpectedBeforeColon, colon) = self.expect(.colon)
} else {
Expand Down