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Include try and await expressions which are parents of a freestanding expression macro in lexicalContext #2724

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Include try and await expressions which are parents of a freestanding expression macro in lexicalContext #2724

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8dbe828
Include try and await expressions which are parents of a freestanding…
stmontgomery Jul 10, 2024
76d026c
Use a wildcard token instead
stmontgomery Jul 10, 2024
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14 changes: 14 additions & 0 deletions Sources/SwiftSyntaxMacros/Syntax+LexicalContext.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,20 @@ extension SyntaxProtocol {
case let freestandingMacro as FreestandingMacroExpansionSyntax:
return Syntax(freestandingMacro.detached) as Syntax

// Try and await are preserved: A freestanding expression macro preceded
// by try or await 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 expression of the try or await is replaced
// with a trivial placeholder, though.
case var tryExpr as TryExprSyntax:
tryExpr = tryExpr.detached
tryExpr.expression = ExprSyntax(TypeExprSyntax(type: IdentifierTypeSyntax(name: .wildcardToken())))
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The wildcard token was chosen arbitrarily here. We don't necessarily have to reassign the expression at all, but I figured it shouldn't be necessary since the macro implementation already has it.

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Arguably we do need to reassign it, otherwise in an expression like this one:

await f(a, b, c, #d)

d is able to see a, b, and c.

return Syntax(tryExpr)
case var awaitExpr as AwaitExprSyntax:
awaitExpr = awaitExpr.detached
awaitExpr.expression = ExprSyntax(TypeExprSyntax(type: IdentifierTypeSyntax(name: .wildcardToken())))
return Syntax(awaitExpr)

default:
return nil
}
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8 changes: 5 additions & 3 deletions Tests/SwiftSyntaxMacroExpansionTest/LexicalContextTests.swift
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Expand Up @@ -531,7 +531,7 @@ final class LexicalContextTests: XCTestCase {
struct S {
let arg: C
var contextDescription: String {
#lexicalContextDescription
try await #lexicalContextDescription
}
}
return S(arg: c)
Expand All @@ -542,7 +542,9 @@ final class LexicalContextTests: XCTestCase {
struct S {
let arg: C
var contextDescription: String {
"""
try await """
await _
try _
contextDescription: String
struct S {}
{ c in
Expand All @@ -551,7 +553,7 @@ final class LexicalContextTests: XCTestCase {
struct S {
let arg: C
var contextDescription: String {
#lexicalContextDescription
try await #lexicalContextDescription
}
}
return S(arg: c)
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