diff --git a/Libraries/StyleSheet/StyleSheetTypes.js b/Libraries/StyleSheet/StyleSheetTypes.js
index 9d4916e66..0964a9446 100644
--- a/Libraries/StyleSheet/StyleSheetTypes.js
+++ b/Libraries/StyleSheet/StyleSheetTypes.js
@@ -18,153 +18,155 @@ export opaque type StyleSheetStyle: number = number;
 export type ColorValue = null | string;
 export type DimensionValue = null | number | string | AnimatedNode;
 
-export type LayoutStyle = {
-  +display?: 'none' | 'flex',
-  +width?: DimensionValue,
-  +height?: DimensionValue,
-  +bottom?: DimensionValue,
-  +end?: DimensionValue,
-  +left?: DimensionValue,
-  +right?: DimensionValue,
-  +start?: DimensionValue,
-  +top?: DimensionValue,
-  +minWidth?: DimensionValue,
-  +maxWidth?: DimensionValue,
-  +minHeight?: DimensionValue,
-  +maxHeight?: DimensionValue,
-  +margin?: DimensionValue,
-  +marginBottom?: DimensionValue,
-  +marginEnd?: DimensionValue,
-  +marginHorizontal?: DimensionValue,
-  +marginLeft?: DimensionValue,
-  +marginRight?: DimensionValue,
-  +marginStart?: DimensionValue,
-  +marginTop?: DimensionValue,
-  +marginVertical?: DimensionValue,
-  +padding?: DimensionValue,
-  +paddingBottom?: DimensionValue,
-  +paddingEnd?: DimensionValue,
-  +paddingHorizontal?: DimensionValue,
-  +paddingLeft?: DimensionValue,
-  +paddingRight?: DimensionValue,
-  +paddingStart?: DimensionValue,
-  +paddingTop?: DimensionValue,
-  +paddingVertical?: DimensionValue,
-  +borderWidth?: number,
-  +borderBottomWidth?: number,
-  +borderEndWidth?: number,
-  +borderLeftWidth?: number,
-  +borderRightWidth?: number,
-  +borderStartWidth?: number,
-  +borderTopWidth?: number,
-  +position?: 'absolute' | 'relative',
-  +flexDirection?: 'row' | 'row-reverse' | 'column' | 'column-reverse',
-  +flexWrap?: 'wrap' | 'nowrap',
-  +justifyContent?:
+export type LayoutStyle = $ReadOnly<{|
+  display?: 'none' | 'flex',
+  width?: DimensionValue,
+  height?: DimensionValue,
+  bottom?: DimensionValue,
+  end?: DimensionValue,
+  left?: DimensionValue,
+  right?: DimensionValue,
+  start?: DimensionValue,
+  top?: DimensionValue,
+  minWidth?: DimensionValue,
+  maxWidth?: DimensionValue,
+  minHeight?: DimensionValue,
+  maxHeight?: DimensionValue,
+  margin?: DimensionValue,
+  marginBottom?: DimensionValue,
+  marginEnd?: DimensionValue,
+  marginHorizontal?: DimensionValue,
+  marginLeft?: DimensionValue,
+  marginRight?: DimensionValue,
+  marginStart?: DimensionValue,
+  marginTop?: DimensionValue,
+  marginVertical?: DimensionValue,
+  padding?: DimensionValue,
+  paddingBottom?: DimensionValue,
+  paddingEnd?: DimensionValue,
+  paddingHorizontal?: DimensionValue,
+  paddingLeft?: DimensionValue,
+  paddingRight?: DimensionValue,
+  paddingStart?: DimensionValue,
+  paddingTop?: DimensionValue,
+  paddingVertical?: DimensionValue,
+  borderWidth?: number,
+  borderBottomWidth?: number,
+  borderEndWidth?: number,
+  borderLeftWidth?: number,
+  borderRightWidth?: number,
+  borderStartWidth?: number,
+  borderTopWidth?: number,
+  position?: 'absolute' | 'relative',
+  flexDirection?: 'row' | 'row-reverse' | 'column' | 'column-reverse',
+  flexWrap?: 'wrap' | 'nowrap',
+  justifyContent?:
     | 'flex-start'
     | 'flex-end'
     | 'center'
     | 'space-between'
     | 'space-around'
     | 'space-evenly',
-  +alignItems?: 'flex-start' | 'flex-end' | 'center' | 'stretch' | 'baseline',
-  +alignSelf?:
+  alignItems?: 'flex-start' | 'flex-end' | 'center' | 'stretch' | 'baseline',
+  alignSelf?:
     | 'auto'
     | 'flex-start'
     | 'flex-end'
     | 'center'
     | 'stretch'
     | 'baseline',
-  +alignContent?:
+  alignContent?:
     | 'flex-start'
     | 'flex-end'
     | 'center'
     | 'stretch'
     | 'space-between'
     | 'space-around',
-  +overflow?: 'visible' | 'hidden' | 'scroll',
-  +flex?: number,
-  +flexGrow?: number,
-  +flexShrink?: number,
-  +flexBasis?: number | string,
-  +aspectRatio?: number,
-  +zIndex?: number,
-  +direction?: 'inherit' | 'ltr' | 'rtl',
-};
+  overflow?: 'visible' | 'hidden' | 'scroll',
+  flex?: number,
+  flexGrow?: number,
+  flexShrink?: number,
+  flexBasis?: number | string,
+  aspectRatio?: number,
+  zIndex?: number,
+  direction?: 'inherit' | 'ltr' | 'rtl',
+|}>;
 
-export type TransformStyle = {
-  +transform?: $ReadOnlyArray<
-    | {+perspective: number | AnimatedNode}
-    | {+rotate: string}
-    | {+rotateX: string}
-    | {+rotateY: string}
-    | {+rotateZ: string}
-    | {+scale: number | AnimatedNode}
-    | {+scaleX: number | AnimatedNode}
-    | {+scaleY: number | AnimatedNode}
-    | {+translateX: number | AnimatedNode}
-    | {+translateY: number | AnimatedNode}
-    | {
+export type TransformStyle = $ReadOnly<{|
+  transform?: $ReadOnlyArray<
+    | {|+perspective: number | AnimatedNode|}
+    | {|+rotate: string|}
+    | {|+rotateX: string|}
+    | {|+rotateY: string|}
+    | {|+rotateZ: string|}
+    | {|+scale: number | AnimatedNode|}
+    | {|+scaleX: number | AnimatedNode|}
+    | {|+scaleY: number | AnimatedNode|}
+    | {|+translateX: number | AnimatedNode|}
+    | {|+translateY: number | AnimatedNode|}
+    | {|
       +translate: [number | AnimatedNode, number | AnimatedNode] | AnimatedNode,
-    }
-    | {+skewX: string}
-    | {+skewY: string}
+    |}
+    | {|+skewX: string|}
+    | {|+skewY: string|}
     // TODO: what is the actual type it expects?
-    | {+matrix: $ReadOnlyArray<number | AnimatedNode> | AnimatedNode},
+    | {|
+      +matrix: $ReadOnlyArray<number | AnimatedNode> | AnimatedNode,
+    |},
   >,
-};
+|}>;
 
-export type ShadowStyle = {
-  +shadowColor?: ColorValue,
-  +shadowOffset?: {
-    +width?: number,
-    +height?: number,
-  },
-  +shadowOpacity?: number | AnimatedNode,
-  +shadowRadius?: number,
-};
+export type ShadowStyle = $ReadOnly<{|
+  shadowColor?: ColorValue,
+  shadowOffset?: $ReadOnly<{|
+    width?: number,
+    height?: number,
+  |}>,
+  shadowOpacity?: number | AnimatedNode,
+  shadowRadius?: number,
+|}>;
 
-export type ViewStyle = {
+export type ViewStyle = $ReadOnly<{|
   ...$Exact<LayoutStyle>,
   ...$Exact<ShadowStyle>,
   ...$Exact<TransformStyle>,
-  +backfaceVisibility?: 'visible' | 'hidden',
-  +backgroundColor?: ColorValue,
-  +borderColor?: ColorValue,
-  +borderBottomColor?: ColorValue,
-  +borderEndColor?: ColorValue,
-  +borderLeftColor?: ColorValue,
-  +borderRightColor?: ColorValue,
-  +borderStartColor?: ColorValue,
-  +borderTopColor?: ColorValue,
-  +borderRadius?: number,
-  +borderBottomEndRadius?: number,
-  +borderBottomLeftRadius?: number,
-  +borderBottomRightRadius?: number,
-  +borderBottomStartRadius?: number,
-  +borderTopEndRadius?: number,
-  +borderTopLeftRadius?: number,
-  +borderTopRightRadius?: number,
-  +borderTopStartRadius?: number,
-  +borderStyle?: 'solid' | 'dotted' | 'dashed',
-  +borderWidth?: number,
-  +borderBottomWidth?: number,
-  +borderEndWidth?: number,
-  +borderLeftWidth?: number,
-  +borderRightWidth?: number,
-  +borderStartWidth?: number,
-  +borderTopWidth?: number,
-  +opacity?: number | AnimatedNode,
-  +elevation?: number,
-};
+  backfaceVisibility?: 'visible' | 'hidden',
+  backgroundColor?: ColorValue,
+  borderColor?: ColorValue,
+  borderBottomColor?: ColorValue,
+  borderEndColor?: ColorValue,
+  borderLeftColor?: ColorValue,
+  borderRightColor?: ColorValue,
+  borderStartColor?: ColorValue,
+  borderTopColor?: ColorValue,
+  borderRadius?: number,
+  borderBottomEndRadius?: number,
+  borderBottomLeftRadius?: number,
+  borderBottomRightRadius?: number,
+  borderBottomStartRadius?: number,
+  borderTopEndRadius?: number,
+  borderTopLeftRadius?: number,
+  borderTopRightRadius?: number,
+  borderTopStartRadius?: number,
+  borderStyle?: 'solid' | 'dotted' | 'dashed',
+  borderWidth?: number,
+  borderBottomWidth?: number,
+  borderEndWidth?: number,
+  borderLeftWidth?: number,
+  borderRightWidth?: number,
+  borderStartWidth?: number,
+  borderTopWidth?: number,
+  opacity?: number | AnimatedNode,
+  elevation?: number,
+|}>;
 
-export type TextStyle = {
+export type TextStyle = $ReadOnly<{|
   ...$Exact<ViewStyle>,
-  +color?: ColorValue,
-  +fontFamily?: string,
-  +fontSize?: number,
-  +fontStyle?: 'normal' | 'italic',
-  +fontWeight?:
+  color?: ColorValue,
+  fontFamily?: string,
+  fontSize?: number,
+  fontStyle?: 'normal' | 'italic',
+  fontWeight?:
     | 'normal'
     | 'bold'
     | '100'
@@ -176,37 +178,40 @@ export type TextStyle = {
     | '700'
     | '800'
     | '900',
-  +fontVariant?: $ReadOnlyArray<
+  fontVariant?: $ReadOnlyArray<
     | 'small-caps'
     | 'oldstyle-nums'
     | 'lining-nums'
     | 'tabular-nums'
     | 'proportional-nums',
   >,
-  +textShadowOffset?: {+width?: number, +height?: number},
-  +textShadowRadius?: number,
-  +textShadowColor?: ColorValue,
-  +letterSpacing?: number,
-  +lineHeight?: number,
-  +textAlign?: 'auto' | 'left' | 'right' | 'center' | 'justify',
-  +textAlignVertical?: 'auto' | 'top' | 'bottom' | 'center',
-  +includeFontPadding?: boolean,
-  +textDecorationLine?:
+  textShadowOffset?: $ReadOnly<{|
+    width?: number,
+    height?: number,
+  |}>,
+  textShadowRadius?: number,
+  textShadowColor?: ColorValue,
+  letterSpacing?: number,
+  lineHeight?: number,
+  textAlign?: 'auto' | 'left' | 'right' | 'center' | 'justify',
+  textAlignVertical?: 'auto' | 'top' | 'bottom' | 'center',
+  includeFontPadding?: boolean,
+  textDecorationLine?:
     | 'none'
     | 'underline'
     | 'line-through'
     | 'underline line-through',
-  +textDecorationStyle?: 'solid' | 'double' | 'dotted' | 'dashed',
-  +textDecorationColor?: ColorValue,
-  +writingDirection?: 'auto' | 'ltr' | 'rtl',
-};
+  textDecorationStyle?: 'solid' | 'double' | 'dotted' | 'dashed',
+  textDecorationColor?: ColorValue,
+  writingDirection?: 'auto' | 'ltr' | 'rtl',
+|}>;
 
-export type ImageStyle = {
+export type ImageStyle = $ReadOnly<{|
   ...$Exact<ViewStyle>,
-  +resizeMode?: 'contain' | 'cover' | 'stretch' | 'center' | 'repeat',
-  +tintColor?: ColorValue,
-  +overlayColor?: string,
-};
+  resizeMode?: 'contain' | 'cover' | 'stretch' | 'center' | 'repeat',
+  tintColor?: ColorValue,
+  overlayColor?: string,
+|}>;
 
 export type Style = {
   ...$Exact<TextStyle>,