Switch suffix text over to a dictionary

The dictionary provides more semantic meaning, that we are mapping
from absolute positions over to the suffix text for each position.

Author: DougGregor

Sources/SwiftDiagnostics/DiagnosticsFormatter.swift

@@ -190,7 +190,7 @@ public struct DiagnosticsFormatter {
     tree: SyntaxType,
     diags: [Diagnostic],
     indentString: String,
-    suffixTexts: [(AbsolutePosition, String)],
+    suffixTexts: [AbsolutePosition: String],
     sourceLocationConverter: SourceLocationConverter? = nil
   ) -> String {
     let slc = sourceLocationConverter ?? SourceLocationConverter(file: fileName ?? "", tree: tree)
@@ -320,7 +320,7 @@ public struct DiagnosticsFormatter {
       tree: tree,
       diags: diags,
       indentString: "",
-      suffixTexts: []
+      suffixTexts: [:]
     )
   }
 

Sources/SwiftDiagnostics/GroupedDiagnostics.swift

@@ -149,14 +149,16 @@ extension GroupedDiagnostics {
 
     let childPadding = String(slc.sourceLines.count + 1).count + 1;
 
-    let childSources: [(AbsolutePosition, String)] = sourceFiles[sourceFileID.id].children.map { childBufferID in
+    // Collect the child sources.
+    var childSources: [AbsolutePosition : String] = [:]
+    for childBufferID in sourceFiles[sourceFileID.id].children {
       let childSource = annotateSource(
         childBufferID,
         formatter: formatter,
         indentString: indentString + String(repeating: " ", count: childPadding) + "│"
       )
 
-      return (sourceFiles[childBufferID.id].parent!.1, childSource)
+      childSources[sourceFiles[childBufferID.id].parent!.1, default: ""].append(childSource)
     }
 
     // If this is a nested source file, draw a box around it.

Sources/SwiftSyntax/AbsolutePosition.swift

@@ -12,7 +12,7 @@
 
 /// An absolute position in a source file as text - the absolute utf8Offset from
 /// the start of the file.
-public struct AbsolutePosition: Comparable {
+public struct AbsolutePosition: Comparable, Hashable {
   public let utf8Offset: Int
 
   static let startOfFile = AbsolutePosition(utf8Offset: 0)