Disallow multiline strings in `#sourceLocation` filename

[kimdv]

Issue Kind

Bad Diagnostic Produced

Source Code

      #sourceLocation(file: """
      test.swift
      other.swift
      """, line: 10)

Is accepted and shouldn't be allowed

Description

No response

[ahoppen]

The same applies to almost all other syntax nodes that contain a StringLiteralExprSyntax.

• AttributeSyntax.arguments (used for @_cdecl and @_semantics)
• AvailabilityLabeledArgumentSyntax.value
• ConventionAttributeArgumentsSyntax.cTypeString
• DocumentationAttributeArgumentSyntax.value
• ExposeAttributeArgumentsSyntax.cxxName
• OpaqueReturnTypeOfAttributeArgumentsSyntax.mangledName
• OriginallyDefinedInAttributeArgumentsSyntax.moduleName
• PoundSourceLocationArgumentsSyntax.fileName
• UnavailableFromAsyncAttributeArgumentsSyntax.message
• UnderscorePrivateAttributeArgumentsSyntax.filename

[ahoppen]

Tracked in Apple’s issue tracker as rdar://113567646

[ahoppen]

Decided that we should allow multi-line string literals here. See swiftlang/swift#71366