Allow some fields to be overridden in strong mode.

For consistency, any field in a class that's meant to be extended can be
overridden.

[email protected], [email protected]

Review URL: https://codereview.chromium.org//1728113002 .

Author: nex3

CHANGELOG.md

@@ -1,3 +1,8 @@
+# 1.2.2
+
+* Allow `SourceSpanException.message`, `SourceSpanFormatException.source`, and
+  `SourceSpanWithContext.context` to be overridden in strong mode.
+
 # 1.2.1
 
 * Fix the declared type of `FileSpan.start` and `FileSpan.end`. In 1.2.0 these

lib/src/span_exception.dart

@@ -6,15 +6,19 @@ import 'span.dart';
 
 /// A class for exceptions that have source span information attached.
 class SourceSpanException implements Exception {
+  // This is a getter so that subclasses can override it.
   /// A message describing the exception.
-  final String message;
+  String get message => _message;
+  final String _message;
 
+  // This is a getter so that subclasses can override it.
   /// The span associated with this exception.
   ///
   /// This may be `null` if the source location can't be determined.
-  final SourceSpan span;
+  SourceSpan get span => _span;
+  final SourceSpan _span;
 
-  SourceSpanException(this.message, this.span);
+  SourceSpanException(this._message, this._span);
 
   /// Returns a string representation of [this].
   ///
@@ -32,10 +36,9 @@ class SourceSpanException implements Exception {
 /// A [SourceSpanException] that's also a [FormatException].
 class SourceSpanFormatException extends SourceSpanException
     implements FormatException {
-  final _source;
-
-  // Subclasses may narrow the type.
+  // This is a getter so that subclasses can override it.
   dynamic get source => _source;
+  final _source;
 
   int get offset => span == null ? null : span.start.offset;
 

lib/src/span_with_context.dart

@@ -8,8 +8,10 @@ import 'utils.dart';
 
 /// A class that describes a segment of source text with additional context.
 class SourceSpanWithContext extends SourceSpanBase {
+  // This is a getter so that subclasses can override it.
   /// Text around the span, which includes the line containing this span.
-  final String context;
+  String get context => _context;
+  final String _context;
 
   /// Creates a new span from [start] to [end] (exclusive) containing [text], in
   /// the given [context].
@@ -20,7 +22,7 @@ class SourceSpanWithContext extends SourceSpanBase {
   /// [text] should start at `start.column` from the beginning of a line in
   /// [context].
   SourceSpanWithContext(
-      SourceLocation start, SourceLocation end, String text, this.context)
+          SourceLocation start, SourceLocation end, String text, this._context)
       : super(start, end, text) {
     if (!context.contains(text)) {
       throw new ArgumentError(

pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_span
-version: 1.2.1
+version: 1.2.2
 author: Dart Team <[email protected]>
 description: A library for identifying source spans and locations.
 homepage: https://github.com/dart-lang/source_span