Validate style in TextField (#24587)

* Validate style in TextField

* Fix analyze problems

* Use assert and move to top

* Simplified assertion

packages/flutter/lib/src/material/text_field.dart

@@ -568,6 +568,12 @@ class _TextFieldState extends State<TextField> with AutomaticKeepAliveClientMixi
     // TODO(jonahwilliams): uncomment out this check once we have migrated tests.
     // assert(debugCheckHasMaterialLocalizations(context));
     assert(debugCheckHasDirectionality(context));
+    assert(
+      !(widget.style != null && widget.style.inherit == false &&
+         (widget.style.fontSize == null || widget.style.textBaseline == null)),
+      'inherit false style must supply fontSize and textBaseline',
+    );
+
     final ThemeData themeData = Theme.of(context);
     final TextStyle style = widget.style ?? themeData.textTheme.subhead;
     final Brightness keyboardAppearance = widget.keyboardAppearance ?? themeData.primaryColorBrightness;

packages/flutter/test/material/text_field_test.dart

@@ -3419,4 +3419,35 @@ void main() {
     await tester.tap(find.byType(TextField));
     expect(tapCount, 0);
   });
+
+  testWidgets('style enforces required fields', (WidgetTester tester) async {
+    Widget buildFrame(TextStyle style) {
+      return MaterialApp(
+        home: Material(
+          child: TextField(
+            style: style,
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(buildFrame(const TextStyle(
+      inherit: false,
+      fontSize: 12.0,
+      textBaseline: TextBaseline.alphabetic,
+    )));
+    expect(tester.takeException(), isNull);
+
+    // With inherit not set to false, will pickup required fields from theme
+    await tester.pumpWidget(buildFrame(const TextStyle(
+      fontSize: 12.0,
+    )));
+    expect(tester.takeException(), isNull);
+
+    await tester.pumpWidget(buildFrame(const TextStyle(
+      inherit: false,
+      fontSize: 12.0,
+    )));
+    expect(tester.takeException(), isNotNull);
+  });
 }