Added identical(a,b) short circuit to Material Library lerp methods (#120829)

Author: HansMuller

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

@@ -204,6 +204,9 @@ class AppBarTheme with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static AppBarTheme lerp(AppBarTheme? a, AppBarTheme? b, double t) {
+    if (identical(a, b) && a != null) {
+      return a;
+    }
     return AppBarTheme(
       backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
       foregroundColor: Color.lerp(a?.foregroundColor, b?.foregroundColor, t),

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

@@ -94,6 +94,9 @@ class BadgeThemeData with Diagnosticable {
 
   /// Linearly interpolate between two [Badge] themes.
   static BadgeThemeData lerp(BadgeThemeData? a, BadgeThemeData? b, double t) {
+    if (identical(a, b) && a != null) {
+      return a;
+    }
     return BadgeThemeData(
       backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
       textColor: Color.lerp(a?.textColor, b?.textColor, t),

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

@@ -94,6 +94,9 @@ class BottomAppBarTheme with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static BottomAppBarTheme lerp(BottomAppBarTheme? a, BottomAppBarTheme? b, double t) {
+    if (identical(a, b) && a != null) {
+      return a;
+    }
     return BottomAppBarTheme(
       color: Color.lerp(a?.color, b?.color, t),
       elevation: lerpDouble(a?.elevation, b?.elevation, t),

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

@@ -174,6 +174,9 @@ class BottomNavigationBarThemeData with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static BottomNavigationBarThemeData lerp(BottomNavigationBarThemeData? a, BottomNavigationBarThemeData? b, double t) {
+    if (identical(a, b) && a != null) {
+      return a;
+    }
     return BottomNavigationBarThemeData(
       backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
       elevation: lerpDouble(a?.elevation, b?.elevation, t),

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

@@ -118,8 +118,8 @@ class BottomSheetThemeData with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static BottomSheetThemeData? lerp(BottomSheetThemeData? a, BottomSheetThemeData? b, double t) {
-    if (a == null && b == null) {
-      return null;
+    if (identical(a, b)) {
+      return a;
     }
     return BottomSheetThemeData(
       backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),

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

@@ -146,8 +146,8 @@ class ButtonBarThemeData with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static ButtonBarThemeData? lerp(ButtonBarThemeData? a, ButtonBarThemeData? b, double t) {
-    if (a == null && b == null) {
-      return null;
+    if (identical(a, b)) {
+      return a;
     }
     return ButtonBarThemeData(
       alignment: t < 0.5 ? a?.alignment : b?.alignment,

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

@@ -492,8 +492,8 @@ class ButtonStyle with Diagnosticable {
 
   /// Linearly interpolate between two [ButtonStyle]s.
   static ButtonStyle? lerp(ButtonStyle? a, ButtonStyle? b, double t) {
-    if (a == null && b == null) {
-      return null;
+    if (identical(a, b)) {
+      return a;
     }
     return ButtonStyle(
       textStyle: MaterialStateProperty.lerp<TextStyle?>(a?.textStyle, b?.textStyle, t, TextStyle.lerp),

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

@@ -114,6 +114,9 @@ class CardTheme with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static CardTheme lerp(CardTheme? a, CardTheme? b, double t) {
+    if (identical(a, b) && a != null) {
+      return a;
+    }
     return CardTheme(
       clipBehavior: t < 0.5 ? a?.clipBehavior : b?.clipBehavior,
       color: Color.lerp(a?.color, b?.color, t),

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

@@ -130,6 +130,9 @@ class CheckboxThemeData with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static CheckboxThemeData lerp(CheckboxThemeData? a, CheckboxThemeData? b, double t) {
+    if (identical(a, b) && a != null) {
+      return a;
+    }
     return CheckboxThemeData(
       mouseCursor: t < 0.5 ? a?.mouseCursor : b?.mouseCursor,
       fillColor: MaterialStateProperty.lerp<Color?>(a?.fillColor, b?.fillColor, t, Color.lerp),
@@ -195,6 +198,9 @@ class CheckboxThemeData with Diagnosticable {
     if (a == null || b == null) {
       return null;
     }
+    if (identical(a, b)) {
+      return a;
+    }
     return BorderSide.lerp(a, b, t);
   }
 }

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

@@ -483,8 +483,8 @@ class ChipThemeData with Diagnosticable {
   ///
   /// {@macro dart.ui.shadow.lerp}
   static ChipThemeData? lerp(ChipThemeData? a, ChipThemeData? b, double t) {
-    if (a == null && b == null) {
-      return null;
+    if (identical(a, b)) {
+      return a;
     }
     return ChipThemeData(
       backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),