[core] Correct boolean function interpolation

2 files changed, 24 insertions, 10 deletions

diff --git a/src/mbgl/util/interpolate.hpp b/src/mbgl/util/interpolate.hpp
index 958b185d5b..ef066377da 100644
--- a/src/mbgl/util/interpolate.hpp
+++ b/src/mbgl/util/interpolate.hpp
@@ -62,6 +62,10 @@ struct Uninterpolated {
     }
 };
 
+template <>
+struct Interpolator<bool>
+    : Uninterpolated {};
+
 template <class T>
 struct Interpolator<T, typename std::enable_if_t<std::is_enum<T>::value>>
     : Uninterpolated {};
diff --git a/test/style/functions.test.cpp b/test/style/functions.test.cpp
index c50787814b..93447a8943 100644
--- a/test/style/functions.test.cpp
+++ b/test/style/functions.test.cpp
@@ -13,17 +13,20 @@ float evaluate(PropertyValue<float> value, float zoom) {
 std::string evaluate(PropertyValue<std::string> value, float zoom) {
     return value.evaluate(PropertyEvaluator<std::string>(PropertyEvaluationParameters(zoom), ""));
 }
+bool evaluate(PropertyValue<bool> value, float zoom) {
+    return value.evaluate(PropertyEvaluator<bool>(PropertyEvaluationParameters(zoom), false));
+}
 
 TEST(Function, Constant) {
-    EXPECT_EQ(2.0f, evaluate(2, 0));
-    EXPECT_EQ(3.8f, evaluate(3.8, 0));
-    EXPECT_EQ(22.0f, evaluate(22, 0));
-    EXPECT_EQ(2.0f, evaluate(2, 4));
-    EXPECT_EQ(3.8f, evaluate(3.8, 4));
-    EXPECT_EQ(22.0f, evaluate(22, 4));
-    EXPECT_EQ(2.0f, evaluate(2, 22));
-    EXPECT_EQ(3.8f, evaluate(3.8, 22));
-    EXPECT_EQ(22.0f, evaluate(22, 22));
+    EXPECT_EQ(2.0f, evaluate(PropertyValue<float>(2.0), 0));
+    EXPECT_EQ(3.8f, evaluate(PropertyValue<float>(3.8), 0));
+    EXPECT_EQ(22.0f, evaluate(PropertyValue<float>(22.0), 0));
+    EXPECT_EQ(2.0f, evaluate(PropertyValue<float>(2.0), 4));
+    EXPECT_EQ(3.8f, evaluate(PropertyValue<float>(3.8), 4));
+    EXPECT_EQ(22.0f, evaluate(PropertyValue<float>(22.0), 4));
+    EXPECT_EQ(2.0f, evaluate(PropertyValue<float>(2.0), 22));
+    EXPECT_EQ(3.8f, evaluate(PropertyValue<float>(3.8), 22));
+    EXPECT_EQ(22.0f, evaluate(PropertyValue<float>(22.0), 22));
 }
 
 TEST(Function, Stops) {
@@ -60,10 +63,17 @@ TEST(Function, Stops) {
     EXPECT_EQ(10, evaluate(slope_4, 8));
 
     // discrete values
-    Function<std::string> discrete_0({{ 3, "string0"}, {6, "string1"}, {9, "string2"}}, 1);
+    Function<std::string> discrete_0({{3, "string0"}, {6, "string1"}, {9, "string2"}}, 1);
     EXPECT_EQ("string0", evaluate(discrete_0, 2));
     EXPECT_EQ("string0", evaluate(discrete_0, 4));
     EXPECT_EQ("string1", evaluate(discrete_0, 7));
     EXPECT_EQ("string2", evaluate(discrete_0, 9));
     EXPECT_EQ("string2", evaluate(discrete_0, 10));
+
+    Function<bool> discreteBool({{1, false}, {3, true}}, 1);
+    EXPECT_EQ(false, evaluate(discreteBool, 0));
+    EXPECT_EQ(false, evaluate(discreteBool, 1));
+    EXPECT_EQ(false, evaluate(discreteBool, 2));
+    EXPECT_EQ(true, evaluate(discreteBool, 3));
+    EXPECT_EQ(true, evaluate(discreteBool, 4));
 }