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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#if compiler(>=6)
public import SwiftSyntax
import SwiftSyntaxBuilder
#else
import SwiftSyntax
import SwiftSyntaxBuilder
#endif
extension SyntaxProtocol {
/// If this syntax node acts as a lexical context from the perspective
/// of a macro, return a new syntax node based on this node that strips all
/// information that isn't supposed to be exposed as a lexical context, such
/// as function bodies or the members of types/extensions.
///
/// Returns `nil` for any syntax node that isn't a lexical context.
public func asMacroLexicalContext() -> Syntax? {
switch Syntax(self).asProtocol(SyntaxProtocol.self) {
// Functions have their body removed.
case var function as WithOptionalCodeBlockSyntax & SyntaxProtocol:
function = function.detached
function.body = nil
return Syntax(function) as Syntax
// Closures have their body removed.
case var closure as ClosureExprSyntax:
closure = closure.detached
closure.statements = CodeBlockItemListSyntax()
return Syntax(closure)
// Nominal types and extensions have their member list cleared out.
case var typeOrExtension as HasTrailingMemberDeclBlock & SyntaxProtocol:
typeOrExtension = typeOrExtension.detached
typeOrExtension.memberBlock = MemberBlockSyntax(members: MemberBlockItemListSyntax())
return Syntax(typeOrExtension) as Syntax
// Subscripts have their accessors removed.
case var subscriptDecl as SubscriptDeclSyntax:
subscriptDecl = subscriptDecl.detached
subscriptDecl.accessorBlock = nil
return Syntax(subscriptDecl)
// Enum cases are fine as-is.
case is EnumCaseElementSyntax:
return Syntax(self.detached)
// Pattern bindings have their accessors and initializer removed.
case var patternBinding as PatternBindingSyntax:
patternBinding = patternBinding.detached
patternBinding.accessorBlock = nil
patternBinding.initializer = nil
return Syntax(patternBinding)
// Freestanding macros are fine as-is because if any arguments change
// the whole macro would have to be re-evaluated.
case let freestandingMacro as FreestandingMacroExpansionSyntax:
return Syntax(freestandingMacro.detached) as Syntax
// `try`, `await`, and `unsafe` are preserved: A freestanding expression
// macro may need to know whether those keywords are present so it can
// propagate them to any expressions in its expansion which were passed as
// arguments to the macro. The sub-expression is replaced with a trivial
// placeholder, though.
case var tryExpr as TryExprSyntax:
tryExpr = tryExpr.detached
tryExpr.expression = ExprSyntax(TypeExprSyntax(type: IdentifierTypeSyntax(name: .wildcardToken())))
return Syntax(tryExpr)
case var awaitExpr as AwaitExprSyntax:
awaitExpr = awaitExpr.detached
awaitExpr.expression = ExprSyntax(TypeExprSyntax(type: IdentifierTypeSyntax(name: .wildcardToken())))
return Syntax(awaitExpr)
case var unsafeExpr as UnsafeExprSyntax:
unsafeExpr = unsafeExpr.detached
unsafeExpr.expression = ExprSyntax(TypeExprSyntax(type: IdentifierTypeSyntax(name: .wildcardToken())))
return Syntax(unsafeExpr)
default:
return nil
}
}
/// Return an array of enclosing lexical contexts for the purpose of macros,
/// from the innermost enclosing lexical context (first in the array) to the
/// outermost. If this syntax node itself is a lexical context, it will be
/// the innermost lexical context.
///
/// - Parameter enclosingSyntax: provides a parent node when the operation
/// has reached the outermost syntax node (i.e., it has no parent), allowing
/// the caller to provide a new syntax node that can continue the walk
/// to collect additional lexical contexts, e.g., from outer macro
/// expansions.
/// - Returns: the array of enclosing lexical contexts.
public func allMacroLexicalContexts(
enclosingSyntax: (Syntax) -> Syntax? = { _ in nil }
) -> [Syntax] {
var parentContexts: [Syntax] = []
var currentNode = Syntax(self)
while let parentNode = currentNode.parent ?? enclosingSyntax(currentNode) {
if let parentContext = parentNode.asMacroLexicalContext() {
parentContexts.append(parentContext)
}
// Unfolded sequence expressions require special handling - effect marker
// nodes like `try`, `await`, and `unsafe` are treated as lexical contexts
// for all the nodes on their right. Cases where they don't end up
// covering nodes to their right in the folded tree are invalid and will
// be diagnosed by the compiler. This matches the compiler's ASTScope
// handling logic.
if let sequence = parentNode.as(SequenceExprSyntax.self) {
var sequenceExprContexts: [Syntax] = []
for elt in sequence.elements {
if elt.range.contains(self.position) {
// `sequenceExprContexts` is built from the top-down, but we
// build the rest of the contexts bottom-up. Reverse for
// consistency.
parentContexts += sequenceExprContexts.reversed()
break
}
var elt = elt
while true {
if let tryElt = elt.as(TryExprSyntax.self) {
sequenceExprContexts.append(tryElt.asMacroLexicalContext()!)
elt = tryElt.expression
continue
}
if let awaitElt = elt.as(AwaitExprSyntax.self) {
sequenceExprContexts.append(awaitElt.asMacroLexicalContext()!)
elt = awaitElt.expression
continue
}
if let unsafeElt = elt.as(UnsafeExprSyntax.self) {
sequenceExprContexts.append(unsafeElt.asMacroLexicalContext()!)
elt = unsafeElt.expression
continue
}
break
}
}
}
currentNode = parentNode
}
return parentContexts
}
}
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