[core] Assert valid range for color components

include/mbgl/util/color.hpp

@@ -2,6 +2,7 @@
 
 #include <mbgl/util/optional.hpp>
 
+#include <cassert>
 #include <string>
 
 namespace mbgl {
@@ -9,6 +10,19 @@ namespace mbgl {
 // Stores a premultiplied color, with all four channels ranging from 0..1
 class Color {
 public:
+    constexpr Color() = default;
+    constexpr Color(float r_, float g_, float b_, float a_)
+        : r(r_), g(g_), b(b_), a(a_) {
+        assert(r_ >= 0.0f);
+        assert(r_ <= 1.0f);
+        assert(g_ >= 0.0f);
+        assert(g_ <= 1.0f);
+        assert(b_ >= 0.0f);
+        assert(b_ <= 1.0f);
+        assert(a_ >= 0.0f);
+        assert(a_ <= 1.0f);
+    }
+
     float r = 0.0f;
     float g = 0.0f;
     float b = 0.0f;
@@ -33,6 +47,8 @@ constexpr bool operator!=(const Color& colorA, const Color& colorB) {
 }
 
 constexpr Color operator*(const Color& color, float alpha) {
+    assert(alpha >= 0.0f);
+    assert(alpha <= 1.0f);
     return {
         color.r * alpha,
         color.g * alpha,