Reimplement style values atop NSExpression (#10726)

* [ios, macos] Import headers, not implementation files

* [core] Added accessors for various expression parameters

Added missing parameter accessors to various expression operator classes, as well as a method on InterpolatorBase and Step that enumerates the stops and their values.

* [ios, macos] Silenced warning in test of error condition

* [ios, macos] Made MGLSphericalPosition boxable

* [ios, macos] Implemented array enumeration during conversion

* [ios, macos] Temporarily ignore heatmap layer type

* [ios, macos] Migrated MGLSymbolStyleLayer.text to NSExpression

MGLSymbolStyleLayer.text is now of type NSExpression instead of MGLStyleValue, as a first step toward migrating the entire layer API from style values to expressions.

Implemented conversions from NSExpression to JSON arrays and vice versa. The most common NSExpression functions are now converted into style expressions, but not all of the most common style expression operators are supported yet.

* [ios, macos] Implemented string coercion

* [ios, macos] Color literals

* [ios, macos] Null constant expressions

* [ios, macos] Convert dictionary literals

* [ios, macos] Interpolation expressions

* [ios, macos] to-boolean, to-number, get from object

* [ios, macos] Variable expressions

Implemented custom expression functions for assigning and referring to variables within the context of an expression. Variables are assigned via a “context dictionary” and applied to an subexpression that is given as another argument to the same expression. Also implemented built-in variable expressions for zoom level and heatmap density.

* [ios, macos] Convert colors, offsets, padding in expressions to JSON objects

* [ios, macos] Expression-based style property getters

Implemented a conversion from mbgl::style::PropertyValues to Objective-C JSON objects, which are then converted to NSExpressions.

* [ios, macos] Consolidated property value–expression conversion in MGLStyleValueTransformer

* [ios, macos] Predicate and expression guide

Extracted documentation about predicates from a documentation comment in MGLVectorStyleLayer.h to a new jazzy guide. Added details about NSExpression support as well. Began updating the “For Style Authors” guide to reflect the transition from style values to expressions.

* [ios, macos] Updated style authoring guide

Updated the Information for Style Authors guide to discuss expressions instead of style functions. Included a table mapping style specification expression operators to NSExpression syntaxes.

* [ios, macos] Migrated codegen templates to expressions

* [ios, macos] Applied expression changes via codegen

Ran make darwin-style-code.

* [macos] Migrated macosapp to expressions

* [ios, macos] Updated style function guide

This guide needs to be thoroughly rewritten, but for now the example code has been migrated to expressions.

* [ios, macos] Eviscerated style function tests

* [ios, macos] Updated changelogs

* [ios] Migrated iosapp to expressions

* [ios, macos] Exposed JSON conversion methods publicly

* [ios, macos] Removed MGLStyleValue, MGLStyleFunction

1 files changed, 206 insertions, 240 deletions

diff --git a/platform/darwin/src/MGLLineStyleLayer.h b/platform/darwin/src/MGLLineStyleLayer.h
index e48951d97b..003f48ae43 100644
--- a/platform/darwin/src/MGLLineStyleLayer.h
+++ b/platform/darwin/src/MGLLineStyleLayer.h
@@ -2,7 +2,6 @@
 // Edit platform/darwin/scripts/generate-style-code.js, then run `make darwin-style-code`.
 
 #import "MGLFoundation.h"
-#import "MGLStyleValue.h"
 #import "MGLVectorStyleLayer.h"
 
 NS_ASSUME_NONNULL_BEGIN
@@ -94,12 +93,11 @@ typedef NS_ENUM(NSUInteger, MGLLineTranslationAnchor) {
  ```swift
  let layer = MGLLineStyleLayer(identifier: "trails-path", source: trails)
  layer.sourceLayerIdentifier = "trails"
- layer.lineWidth = MGLStyleValue(interpolationMode: .exponential,
-                                 cameraStops: [14: MGLStyleValue(rawValue: 2),
-                                               18: MGLStyleValue(rawValue: 20)],
-                                 options: [.interpolationBase: 1.5])
- layer.lineColor = MGLStyleValue(rawValue: .brown)
- layer.lineCap = MGLStyleValue(rawValue: NSValue(mglLineCap: .round))
+ layer.lineWidth = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.5, %@)",
+                                [14: 2,
+                                 18: 20])
+ layer.lineColor = NSExpression(forConstantValue: UIColor.brown)
+ layer.lineCap = NSExpression(forConstantValue: "round")
  layer.predicate = NSPredicate(format: "%K == %@", "trail-type", "mountain-biking")
  mapView.style?.addLayer(layer)
  ```
@@ -127,82 +125,99 @@ MGL_EXPORT
 /**
  The display of line endings.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSValue` object containing `MGLLineCapButt`. Set this property to `nil` to
- reset it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of
- `MGLInterpolationModeInterval`
+ The default value of this property is an expression that evaluates to `butt`.
+ Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant `MGLLineCap` values
+ * Any of the following constant string values:
+   * `butt`: A cap with a squared-off end which is drawn to the exact endpoint
+ of the line.
+   * `round`: A cap with a rounded end which is drawn beyond the endpoint of the
+ line at a radius of one-half of the line's width and centered on the endpoint
+ of the line.
+   * `square`: A cap with a squared-off end which is drawn beyond the endpoint
+ of the line at a distance of one-half of the line's width.
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Step functions applied to the `$zoomLevel` variable
+ 
+ This property does not support applying interpolation functions to the
+ `$zoomLevel` variable or applying interpolation or step functions to feature
+ attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineCap;
+@property (nonatomic, null_resettable) NSExpression *lineCap;
 
 /**
  The display of lines when joining.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSValue` object containing `MGLLineJoinMiter`. Set this property to `nil` to
- reset it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ The default value of this property is an expression that evaluates to `miter`.
+ Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant `MGLLineJoin` values
+ * Any of the following constant string values:
+   * `bevel`: A join with a squared-off end which is drawn beyond the endpoint
+ of the line at a distance of one-half of the line's width.
+   * `round`: A join with a rounded end which is drawn beyond the endpoint of
+ the line at a radius of one-half of the line's width and centered on the
+ endpoint of the line.
+   * `miter`: A join with a sharp, angled corner which is drawn with the outer
+ sides beyond the endpoint of the path until they meet.
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineJoin;
+@property (nonatomic, null_resettable) NSExpression *lineJoin;
 
 /**
  Used to automatically convert miter joins to bevel joins for sharp angles.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `2`. Set this property to `nil` to reset
- it to the default value.
+ The default value of this property is an expression that evaluates to the float
+ `2`. Set this property to `nil` to reset it to the default value.
  
  This property is only applied to the style if `lineJoin` is set to an
- `MGLStyleValue` object containing an `NSValue` object containing
- `MGLLineJoinMiter`. Otherwise, it is ignored.
+ expression that evaluates to `miter`. Otherwise, it is ignored.
  
- You can set this property to an instance of:
+ You can set this property to an expression containing any of the following:
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable
+ 
+ This property does not support applying interpolation or step functions to
+ feature attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineMiterLimit;
+@property (nonatomic, null_resettable) NSExpression *lineMiterLimit;
 
 /**
  Used to automatically convert round joins to miter joins for shallow angles.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `1.05`. Set this property to `nil` to
- reset it to the default value.
+ The default value of this property is an expression that evaluates to the float
+ `1.05`. Set this property to `nil` to reset it to the default value.
  
  This property is only applied to the style if `lineJoin` is set to an
- `MGLStyleValue` object containing an `NSValue` object containing
- `MGLLineJoinRound`. Otherwise, it is ignored.
+ expression that evaluates to `round`. Otherwise, it is ignored.
+ 
+ You can set this property to an expression containing any of the following:
  
- You can set this property to an instance of:
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
+ This property does not support applying interpolation or step functions to
+ feature attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineRoundLimit;
+@property (nonatomic, null_resettable) NSExpression *lineRoundLimit;
 
 #pragma mark - Accessing the Paint Attributes
 
@@ -211,27 +226,19 @@ MGL_EXPORT
  
  This property is measured in points.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `0`. Set this property to `nil` to reset
- it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ The default value of this property is an expression that evaluates to the float
+ `0`. Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineBlur;
+@property (nonatomic, null_resettable) NSExpression *lineBlur;
 
 /**
  The transition affecting any changes to this layer’s `lineBlur` property.
@@ -240,63 +247,26 @@ MGL_EXPORT
 */
 @property (nonatomic) MGLTransition lineBlurTransition;
 
-#if TARGET_OS_IPHONE
 /**
  The color with which the line will be drawn.
  
- The default value of this property is an `MGLStyleValue` object containing
+ The default value of this property is an expression that evaluates to
  `UIColor.blackColor`. Set this property to `nil` to reset it to the default
  value.
  
  This property is only applied to the style if `linePattern` is set to `nil`.
  Otherwise, it is ignored.
  
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
- */
-@property (nonatomic, null_resettable) MGLStyleValue<UIColor *> *lineColor;
-#else
-/**
- The color with which the line will be drawn.
- 
- The default value of this property is an `MGLStyleValue` object containing
- `NSColor.blackColor`. Set this property to `nil` to reset it to the default
- value.
- 
- This property is only applied to the style if `linePattern` is set to `nil`.
- Otherwise, it is ignored.
+ You can set this property to an expression containing any of the following:
  
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ * Constant `UIColor` values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSColor *> *lineColor;
-#endif
+@property (nonatomic, null_resettable) NSExpression *lineColor;
 
 /**
  The transition affecting any changes to this layer’s `lineColor` property.
@@ -319,13 +289,19 @@ MGL_EXPORT
  href="https://www.mapbox.com/mapbox-gl-style-spec/#paint-line-dasharray"><code>line-dasharray</code></a>
  layout property in the Mapbox Style Specification.
  
- You can set this property to an instance of:
+ You can set this property to an expression containing any of the following:
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of
- `MGLInterpolationModeInterval`
+ * Constant array values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Step functions applied to the `$zoomLevel` variable
+ 
+ This property does not support applying interpolation functions to the
+ `$zoomLevel` variable or applying interpolation or step functions to feature
+ attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSArray<NSNumber *> *> *lineDashPattern;
+@property (nonatomic, null_resettable) NSExpression *lineDashPattern;
 
 /**
  The transition affecting any changes to this layer’s `lineDashPattern` property.
@@ -334,7 +310,7 @@ MGL_EXPORT
 */
 @property (nonatomic) MGLTransition lineDashPatternTransition;
 
-@property (nonatomic, null_resettable) MGLStyleValue<NSArray<NSNumber *> *> *lineDasharray __attribute__((unavailable("Use lineDashPattern instead.")));
+@property (nonatomic, null_resettable) NSExpression *lineDasharray __attribute__((unavailable("Use lineDashPattern instead.")));
 
 /**
  Draws a line casing outside of a line's actual path. Value indicates the width
@@ -342,27 +318,19 @@ MGL_EXPORT
  
  This property is measured in points.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `0`. Set this property to `nil` to reset
- it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ The default value of this property is an expression that evaluates to the float
+ `0`. Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineGapWidth;
+@property (nonatomic, null_resettable) NSExpression *lineGapWidth;
 
 /**
  The transition affecting any changes to this layer’s `lineGapWidth` property.
@@ -379,27 +347,19 @@ MGL_EXPORT
  
  This property is measured in points.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `0`. Set this property to `nil` to reset
- it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ The default value of this property is an expression that evaluates to the float
+ `0`. Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineOffset;
+@property (nonatomic, null_resettable) NSExpression *lineOffset;
 
 /**
  The transition affecting any changes to this layer’s `lineOffset` property.
@@ -411,27 +371,19 @@ MGL_EXPORT
 /**
  The opacity at which the line will be drawn.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `1`. Set this property to `nil` to reset
- it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ The default value of this property is an expression that evaluates to the float
+ `1`. Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineOpacity;
+@property (nonatomic, null_resettable) NSExpression *lineOpacity;
 
 /**
  The transition affecting any changes to this layer’s `lineOpacity` property.
@@ -444,13 +396,19 @@ MGL_EXPORT
  Name of image in style images to use for drawing image lines. For seamless
  patterns, image width must be a factor of two (2, 4, 8, ..., 512).
  
- You can set this property to an instance of:
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant string values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Step functions applied to the `$zoomLevel` variable
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of
- `MGLInterpolationModeInterval`
+ This property does not support applying interpolation functions to the
+ `$zoomLevel` variable or applying interpolation or step functions to feature
+ attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSString *> *linePattern;
+@property (nonatomic, null_resettable) NSExpression *linePattern;
 
 /**
  The transition affecting any changes to this layer’s `linePattern` property.
@@ -465,7 +423,7 @@ MGL_EXPORT
  
  This property is measured in points.
  
- The default value of this property is an `MGLStyleValue` object containing an
+ The default value of this property is an expression that evaluates to an
  `NSValue` object containing a `CGVector` struct set to 0 points rightward and 0
  points downward. Set this property to `nil` to reset it to the default value.
  
@@ -473,21 +431,25 @@ MGL_EXPORT
  href="https://www.mapbox.com/mapbox-gl-style-spec/#paint-line-translate"><code>line-translate</code></a>
  layout property in the Mapbox Style Specification.
  
- You can set this property to an instance of:
+ You can set this property to an expression containing any of the following:
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
+ * Constant `CGVector` values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable
+ 
+ This property does not support applying interpolation or step functions to
+ feature attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineTranslation;
+@property (nonatomic, null_resettable) NSExpression *lineTranslation;
 #else
 /**
  The geometry's offset.
  
  This property is measured in points.
  
- The default value of this property is an `MGLStyleValue` object containing an
+ The default value of this property is an expression that evaluates to an
  `NSValue` object containing a `CGVector` struct set to 0 points rightward and 0
  points upward. Set this property to `nil` to reset it to the default value.
  
@@ -495,14 +457,18 @@ MGL_EXPORT
  href="https://www.mapbox.com/mapbox-gl-style-spec/#paint-line-translate"><code>line-translate</code></a>
  layout property in the Mapbox Style Specification.
  
- You can set this property to an instance of:
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant `CGVector` values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
+ This property does not support applying interpolation or step functions to
+ feature attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineTranslation;
+@property (nonatomic, null_resettable) NSExpression *lineTranslation;
 #endif
 
 /**
@@ -512,14 +478,13 @@ MGL_EXPORT
 */
 @property (nonatomic) MGLTransition lineTranslationTransition;
 
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineTranslate __attribute__((unavailable("Use lineTranslation instead.")));
+@property (nonatomic, null_resettable) NSExpression *lineTranslate __attribute__((unavailable("Use lineTranslation instead.")));
 
 /**
  Controls the frame of reference for `lineTranslation`.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSValue` object containing `MGLLineTranslationAnchorMap`. Set this property to
- `nil` to reset it to the default value.
+ The default value of this property is an expression that evaluates to `map`.
+ Set this property to `nil` to reset it to the default value.
  
  This property is only applied to the style if `lineTranslation` is non-`nil`.
  Otherwise, it is ignored.
@@ -528,42 +493,43 @@ MGL_EXPORT
  href="https://www.mapbox.com/mapbox-gl-style-spec/#paint-line-translate-anchor"><code>line-translate-anchor</code></a>
  layout property in the Mapbox Style Specification.
  
- You can set this property to an instance of:
+ You can set this property to an expression containing any of the following:
  
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of
- `MGLInterpolationModeInterval`
+ * Constant `MGLLineTranslationAnchor` values
+ * Any of the following constant string values:
+   * `map`: The line is translated relative to the map.
+   * `viewport`: The line is translated relative to the viewport.
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Step functions applied to the `$zoomLevel` variable
+ 
+ This property does not support applying interpolation functions to the
+ `$zoomLevel` variable or applying interpolation or step functions to feature
+ attributes.
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineTranslationAnchor;
+@property (nonatomic, null_resettable) NSExpression *lineTranslationAnchor;
 
-@property (nonatomic, null_resettable) MGLStyleValue<NSValue *> *lineTranslateAnchor __attribute__((unavailable("Use lineTranslationAnchor instead.")));
+@property (nonatomic, null_resettable) NSExpression *lineTranslateAnchor __attribute__((unavailable("Use lineTranslationAnchor instead.")));
 
 /**
  Stroke thickness.
  
  This property is measured in points.
  
- The default value of this property is an `MGLStyleValue` object containing an
- `NSNumber` object containing the float `1`. Set this property to `nil` to reset
- it to the default value.
- 
- You can set this property to an instance of:
- 
- * `MGLConstantStyleValue`
- * `MGLCameraStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
- * `MGLSourceStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
-   * `MGLInterpolationModeIdentity`
- * `MGLCompositeStyleFunction` with an interpolation mode of:
-   * `MGLInterpolationModeExponential`
-   * `MGLInterpolationModeInterval`
-   * `MGLInterpolationModeCategorical`
+ The default value of this property is an expression that evaluates to the float
+ `1`. Set this property to `nil` to reset it to the default value.
+ 
+ You can set this property to an expression containing any of the following:
+ 
+ * Constant numeric values
+ * Predefined functions, including mathematical and string operators
+ * Conditional expressions
+ * Variable assignments and references to assigned variables
+ * Interpolation and step functions applied to the `$zoomLevel` variable and/or
+ feature attributes
  */
-@property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *lineWidth;
+@property (nonatomic, null_resettable) NSExpression *lineWidth;
 
 /**
  The transition affecting any changes to this layer’s `lineWidth` property.