Relax precondition in postProcessMultilineStringLiteral

The only place where we were dropping unexpected tokens or trivia around a string segment was when inferring the indentation of the closing quote. Instead of having a precondition, add the conditions that the last segment doesn’t have any of these here and fall back to the same logic that is used when the indentaiton could not be inferred.

Fixes #3097

Author: ahoppen

Sources/SwiftParser/StringLiterals.swift

@@ -340,22 +340,6 @@ extension Parser {
     unexpectedBeforeClosingQuote: [RawTokenSyntax],
     closingQuote: RawTokenSyntax
   ) {
-    // -------------------------------------------------------------------------
-    // Precondition
-
-    precondition(
-      allSegments.allSatisfy {
-        if case .stringSegment(let segment) = $0 {
-          return segment.unexpectedBeforeContent == nil
-            && segment.unexpectedAfterContent == nil
-            && segment.content.leadingTriviaByteLength == 0
-        } else {
-          return true
-        }
-      },
-      "String segment produced by the lexer should not have unexpected text or trivia because we would drop it during post-processing"
-    )
-
     // -------------------------------------------------------------------------
     // Variables
 
@@ -395,6 +379,9 @@ extension Parser {
     // Parse indentation of the closing quote
 
     if let lastSegment,
+      lastSegment.unexpectedBeforeContent == nil,
+      lastSegment.unexpectedAfterContent == nil,
+      lastSegment.content.leadingTriviaByteLength == 0,
       let parsedTrivia = parseIndentationTrivia(text: lastSegment.content.tokenText)
     {
       indentationTrivia = parsedTrivia
@@ -409,10 +396,9 @@ extension Parser {
         arena: self.arena
       )
     } else {
-      if let lastSegment = lastSegment {
-        indentationTrivia = TriviaParser.parseTrivia(lastSegment.content.tokenText, position: .leading).prefix(while: {
-          $0.isIndentationWhitespace
-        })
+      if let lastSegment {
+        indentationTrivia = TriviaParser.parseTrivia(lastSegment.content.tokenText, position: .leading)
+          .prefix(while: \.isIndentationWhitespace)
         let indentationByteLength = indentationTrivia.reduce(0, { $0 + $1.byteLength })
         indentation = SyntaxText(rebasing: lastSegment.content.tokenText[0..<indentationByteLength])
         middleSegments.append(.stringSegment(lastSegment))
@@ -703,10 +689,7 @@ extension Parser {
       }
     }
 
-    let (unexpectedBetweenSegmentAndCloseQuote, closeQuote) = self.expect(
-      anyIn: SimpleStringLiteralExprSyntax.ClosingQuoteOptions.self,
-      default: openQuote.closeTokenKind
-    )
+    let (unexpectedBetweenSegmentAndCloseQuote, closeQuote) = self.expect(openQuote.closeTokenKind.spec)
     let closeDelimiter = self.consume(if: .rawStringPoundDelimiter)
 
     if openQuote.tokenKind == .multilineStringQuote, !openQuote.isMissing, !closeQuote.isMissing {

Tests/SwiftParserTest/translated/StringLiteralEofTests.swift

@@ -243,4 +243,37 @@ final class StringLiteralEofTests: ParserTestCase {
         """##
     )
   }
+
+  func testSimpleMultilineStringLiteralWith() {
+    assertParse(
+      #"""
+      #sourceLocation1️⃣(file: 2️⃣"""3️⃣\(4️⃣"5️⃣
+      """#,
+      diagnostics: [
+        DiagnosticSpec(locationMarker: "3️⃣", message: "argument cannot be an interpolated string literal"),
+        DiagnosticSpec(
+          locationMarker: "4️⃣",
+          message: #"expected '"""' to end simple string literal"#,
+          notes: [NoteSpec(locationMarker: "2️⃣", message: #"to match this opening '"""'"#)],
+          fixIts: [#"insert '"""'"#]
+        ),
+        DiagnosticSpec(
+          locationMarker: "4️⃣",
+          message: "expected ', line:' and line number in '#sourceLocation' arguments",
+          fixIts: ["insert ', line:' and line number"]
+        ),
+        DiagnosticSpec(
+          locationMarker: "4️⃣",
+          message: "expected ')' in '#sourceLocation' directive",
+          notes: [NoteSpec(locationMarker: "1️⃣", message: "to match this opening '('")],
+          fixIts: ["insert ')'"]
+        ),
+        DiagnosticSpec(locationMarker: "4️⃣", message: "extra tokens following the #sourceLocation directive"),
+      ],
+      fixedSource: #"""
+        #sourceLocation(file: """\(
+        """, line: <#integer literal#>)"
+        """#
+    )
+  }
 }