Make SkTFitsIn and SkTo constexpr.

Because what can be better than marking things that can be constexpr as
constexpr. Also, I have a change where this would be nice to have.

Change-Id: Ie313b19d1930b98ddcd60cc17a320971625f18e3
Reviewed-on: https://skia-review.googlesource.com/60862
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>

2 files changed, 8 insertions, 8 deletions

diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index 59bdaaa90c..15a03d8fab 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -206,9 +206,9 @@ typedef unsigned U16CPU;
 typedef uint8_t SkBool8;
 
 #include "../private/SkTFitsIn.h"
-template <typename D, typename S> D SkTo(S s) {
-    SkASSERT(SkTFitsIn<D>(s));
-    return static_cast<D>(s);
+template <typename D, typename S> constexpr D SkTo(S s) {
+    return SkASSERT(SkTFitsIn<D>(s)),
+           static_cast<D>(s);
 }
 #define SkToS8(x)    SkTo<int8_t>(x)
 #define SkToU8(x)    SkTo<uint8_t>(x)
diff --git a/include/private/SkTFitsIn.h b/include/private/SkTFitsIn.h
index a4ea30b022..a889807360 100644
--- a/include/private/SkTFitsIn.h
+++ b/include/private/SkTFitsIn.h
@@ -66,7 +66,7 @@ template <typename A, typename B> struct SkTHasMoreDigits
  *  Used when it is statically known that source values are in the range of the Destination.
  */
 template <typename S> struct SkTInRange_True {
-    static bool fits(S) {
+    static constexpr bool fits(S) {
         return true;
     }
 };
@@ -75,7 +75,7 @@ template <typename S> struct SkTInRange_True {
  *  This is not valid for uX -> sx and sx -> uX conversions.
  */
 template <typename D, typename S> struct SkTInRange_Cast {
-    static bool fits(S s) {
+    static constexpr bool fits(S s) {
         using S_is_bigger = SkTHasMoreDigits<S, D>;
         using D_is_bigger = SkTHasMoreDigits<D, S>;
 
@@ -95,7 +95,7 @@ template <typename D, typename S> struct SkTInRange_Cast {
  *  Assumes that Max(S) >= Max(D).
  */
 template <typename D, typename S> struct SkTInRange_LE_MaxD {
-    static bool fits(S s) {
+    static constexpr bool fits(S s) {
         using precondition = SkTHasMoreDigits<S, D>;
         static_assert(precondition::value, "maxS < maxD");
 
@@ -106,7 +106,7 @@ template <typename D, typename S> struct SkTInRange_LE_MaxD {
 
 /** Tests if the source value >= 0. */
 template <typename D, typename S> struct SkTInRange_GE_Zero {
-    static bool fits(S s) {
+    static constexpr bool fits(S s) {
         return static_cast<S>(0) <= s;
     }
 };
@@ -197,7 +197,7 @@ template <typename T> struct underlying_type<T, false> {
 } // namespace sktfitsin
 
 /** Returns true if the integer source value 's' will fit in the integer destination type 'D'. */
-template <typename D, typename S> inline bool SkTFitsIn(S s) {
+template <typename D, typename S> constexpr inline bool SkTFitsIn(S s) {
     static_assert(std::is_integral<S>::value || std::is_enum<S>::value, "S must be integral.");
     static_assert(std::is_integral<D>::value || std::is_enum<D>::value, "D must be integral.");