From a4c82b8a3b5e48f3bbccf32be80d45ca78d51515 Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Fri, 28 Oct 2016 14:55:07 -0700
Subject: [core] operator bool() must always be explicit

Otherwise, it can participate in unexpected conversions. Case in point: GlyphSet::insert was comparing the result of GlyphMetrics::operator bool() where it wanted to use operator==.
---
 include/mbgl/util/size.hpp |  2 +-
 src/mbgl/text/glyph.hpp    | 14 +++++++++++---
 src/mbgl/text/shaping.hpp  |  2 +-
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/mbgl/util/size.hpp b/include/mbgl/util/size.hpp
index c0e2fd8180..1af85bcff5 100644
--- a/include/mbgl/util/size.hpp
+++ b/include/mbgl/util/size.hpp
@@ -13,7 +13,7 @@ public:
     constexpr Size(const uint32_t width_, const uint32_t height_) : width(width_), height(height_) {
     }
 
-    constexpr operator bool() const {
+    constexpr explicit operator bool() const {
         return width > 0 && height > 0;
     }
 
diff --git a/src/mbgl/text/glyph.hpp b/src/mbgl/text/glyph.hpp
index 975dc4ad23..a333f68ff4 100644
--- a/src/mbgl/text/glyph.hpp
+++ b/src/mbgl/text/glyph.hpp
@@ -14,7 +14,7 @@ namespace mbgl {
 GlyphRange getGlyphRange(char32_t glyph);
 
 struct GlyphMetrics {
-    operator bool() const {
+    explicit operator bool() const {
         return !(width == 0 && height == 0 && advance == 0);
     }
 
@@ -27,12 +27,20 @@ struct GlyphMetrics {
 
 };
 
+inline bool operator==(const GlyphMetrics& lhs, const GlyphMetrics& rhs) {
+    return lhs.width == rhs.width &&
+        lhs.height == rhs.height &&
+        lhs.left == rhs.left &&
+        lhs.top == rhs.top &&
+        lhs.advance == rhs.advance;
+}
+
 struct Glyph {
     explicit Glyph() : rect(0, 0, 0, 0), metrics() {}
     explicit Glyph(Rect<uint16_t> rect_, GlyphMetrics metrics_)
         : rect(std::move(rect_)), metrics(std::move(metrics_)) {}
 
-    operator bool() const {
+    explicit operator bool() const {
         return metrics || rect.hasArea();
     }
 
@@ -64,7 +72,7 @@ class Shaping {
     int32_t left;
     int32_t right;
 
-    operator bool() const { return !positionedGlyphs.empty(); }
+    explicit operator bool() const { return !positionedGlyphs.empty(); }
 };
 
 class SDFGlyph {
diff --git a/src/mbgl/text/shaping.hpp b/src/mbgl/text/shaping.hpp
index cd5e8105fd..7852f710f1 100644
--- a/src/mbgl/text/shaping.hpp
+++ b/src/mbgl/text/shaping.hpp
@@ -26,7 +26,7 @@ class PositionedIcon {
         float left = 0;
         float right = 0;
 
-        operator bool() const { return image && (*image).pos.hasArea(); }
+        explicit operator bool() const { return image && (*image).pos.hasArea(); }
 };
 
 PositionedIcon shapeIcon(const SpriteAtlasElement& image, const style::SymbolLayoutProperties&);
-- 
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