fix constexpr ig

Author: Tr1NgleDev

glm/detail/type_vec2.inl

@@ -106,14 +106,60 @@ namespace glm
 	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T & vec<2, T, Q>::operator[](typename vec<2, T, Q>::length_type i)
 	{
 		GLM_ASSERT_LENGTH(i, this->length());
+
+#		if GLM_LANG & GLM_LANG_CXX14_FLAG || GLM_LANG & GLM_LANG_CXX17_FLAG
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		if (std::is_constant_evaluated())
+		{
+#		endif
+			switch (i)
+			{
+			default:
+			case 0:
+				return x;
+			case 1:
+				return y;
+			}
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		}
+		else
+		{
+			return (&x)[i];
+		}
+#		endif
+#		else
 		return (&x)[i];
+#		endif
 	}
 
 	template<typename T, qualifier Q>
 	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T const& vec<2, T, Q>::operator[](typename vec<2, T, Q>::length_type i) const
 	{
 		GLM_ASSERT_LENGTH(i, this->length());
+
+#		if GLM_LANG & GLM_LANG_CXX14_FLAG || GLM_LANG & GLM_LANG_CXX17_FLAG
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		if (std::is_constant_evaluated())
+		{
+#		endif
+			switch (i)
+			{
+			default:
+			case 0:
+				return x;
+			case 1:
+				return y;
+			}
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		}
+		else
+		{
+			return (&x)[i];
+		}
+#		endif
+#		else
 		return (&x)[i];
+#		endif
 	}
 
 	// -- Unary arithmetic operators --

glm/detail/type_vec3.inl

@@ -171,14 +171,63 @@ namespace glm
 	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T & vec<3, T, Q>::operator[](typename vec<3, T, Q>::length_type i)
 	{
 		GLM_ASSERT_LENGTH(i, this->length());
+#		if GLM_LANG & GLM_LANG_CXX14_FLAG || GLM_LANG & GLM_LANG_CXX17_FLAG
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		if (std::is_constant_evaluated())
+		{
+#		endif
+			switch (i)
+			{
+			default:
+			case 0:
+				return x;
+			case 1:
+				return y;
+			case 2:
+				return z;
+			}
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		}
+		else
+		{
+			return (&x)[i];
+		}
+#		endif
+#		else
 		return (&x)[i];
+#		endif
 	}
 
 	template<typename T, qualifier Q>
 	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T const& vec<3, T, Q>::operator[](typename vec<3, T, Q>::length_type i) const
 	{
 		GLM_ASSERT_LENGTH(i, this->length());
+
+#		if GLM_LANG & GLM_LANG_CXX14_FLAG || GLM_LANG & GLM_LANG_CXX17_FLAG
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		if (std::is_constant_evaluated())
+		{
+#		endif
+			switch (i)
+			{
+			default:
+			case 0:
+				return x;
+			case 1:
+				return y;
+			case 2:
+				return z;
+			}
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		}
+		else
+		{
+			return (&x)[i];
+		}
+#		endif
+#		else
 		return (&x)[i];
+#		endif
 	}
 
 	// -- Unary arithmetic operators --

glm/detail/type_vec4.inl

@@ -362,14 +362,68 @@ namespace detail
 	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T& vec<4, T, Q>::operator[](typename vec<4, T, Q>::length_type i)
 	{
 		GLM_ASSERT_LENGTH(i, this->length());
-		return (&x)[i];
+
+#		if GLM_LANG & GLM_LANG_CXX14_FLAG || GLM_LANG & GLM_LANG_CXX17_FLAG
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+			if (std::is_constant_evaluated())
+			{
+#		endif
+				switch (i)
+				{
+				default:
+				case 0:
+					return x;
+				case 1:
+					return y;
+				case 2:
+					return z;
+				case 3:
+					return w;
+				}
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+			}
+			else
+			{
+				return (&x)[i];
+			}
+#		endif
+#		else
+				return (&x)[i];
+#		endif
 	}
 
 	template<typename T, qualifier Q>
 	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T const& vec<4, T, Q>::operator[](typename vec<4, T, Q>::length_type i) const
 	{
 		GLM_ASSERT_LENGTH(i, this->length());
+
+#		if GLM_LANG & GLM_LANG_CXX14_FLAG || GLM_LANG & GLM_LANG_CXX17_FLAG
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		if (std::is_constant_evaluated())
+		{
+#			endif
+			switch (i)
+			{
+			default:
+			case 0:
+				return x;
+			case 1:
+				return y;
+			case 2:
+				return z;
+			case 3:
+				return w;
+			}
+#		if GLM_LANG & GLM_LANG_CXX20_FLAG
+		}
+		else
+		{
+			return (&x)[i];
+		}
+#		endif
+#		else
 		return (&x)[i];
+#		endif
 	}
 
 	// -- Unary arithmetic operators --