[null-safety] fix soundness of Paragraph._addPlaceholder (#21994)

Jonah Williams · web-flow · commit 6ce33dd4a9fd · 2020-10-20T09:57:59.000-07:00
diff --git a/lib/ui/text.dart b/lib/ui/text.dart
@@ -2242,7 +2242,7 @@ class ParagraphBuilder extends NativeFieldWrapperClass2 {
     _placeholderCount++;
     _placeholderScales.add(scale);
   }
-  String _addPlaceholder(double width, double height, int alignment, double baselineOffset, int? baseline) native 'ParagraphBuilder_addPlaceholder';
+  String? _addPlaceholder(double width, double height, int alignment, double baselineOffset, int? baseline) native 'ParagraphBuilder_addPlaceholder';
 
   /// Applies the given paragraph style and returns a [Paragraph] containing the
   /// added text and associated styling.

Original file line number	Diff line number	Diff line change
`@@ -2242,7 +2242,7 @@ class ParagraphBuilder extends NativeFieldWrapperClass2 {`
`2242`	`2242`	`_placeholderCount++;`
`2243`	`2243`	`_placeholderScales.add(scale);`
`2244`	`2244`	`}`
`2245`		`- String _addPlaceholder(double width, double height, int alignment, double baselineOffset, int? baseline) native 'ParagraphBuilder_addPlaceholder';`
	`2245`	`+ String? _addPlaceholder(double width, double height, int alignment, double baselineOffset, int? baseline) native 'ParagraphBuilder_addPlaceholder';`
`2246`	`2246`
`2247`	`2247`	`/// Applies the given paragraph style and returns a [Paragraph] containing the`
`2248`	`2248`	`/// added text and associated styling.`