Fix for #724

This now throws early for an invalid call, rather than a currently confusing server message to users (see #724 fo details).

StackExchange.Redis.Tests/GeoTests.cs

 using Xunit;
 using System;
 using Xunit.Abstractions;
+using System.Threading.Tasks;
 
 namespace StackExchange.Redis.Tests
 {
@@ -173,7 +174,7 @@ public void GeoRadius()
         }
 
         [Fact]
-        public void GeoRadiusOverloads()
+        public async Task GeoRadiusOverloads()
         {
             using (var conn = Create())
             {
@@ -185,13 +186,19 @@ public void GeoRadiusOverloads()
                 Assert.True(db.GeoAdd(key, -1.759925, 52.19493, "steve"));
                 Assert.True(db.GeoAdd(key, -3.360655, 54.66395, "dave"));
 
-                // Invalid overload, but due to implcit double => RedisValue conversion it happily calls
-                var ex = Assert.Throws<RedisServerException>(() => db.GeoRadius(key, -1.759925, 52.19493, GeoUnit.Miles, 500, Order.Ascending, GeoRadiusOptions.WithDistance));
-                Assert.Equal("ERR could not decode requested zset member", ex.Message);
+                // Invalid overload
+                // Since this would throw ERR could not decode requested zset member, we catch and return something more useful to the user earlier.
+                var ex = Assert.Throws<ArgumentException>(() => db.GeoRadius(key, -1.759925, 52.19493, GeoUnit.Miles, 500, Order.Ascending, GeoRadiusOptions.WithDistance));
+                Assert.Equal("Member should not be a double, you likely want the GeoRadius(RedisKey, double, double, ...) overload.\r\nParameter name: member", ex.Message);
+                ex = await Assert.ThrowsAsync<ArgumentException>(() => db.GeoRadiusAsync(key, -1.759925, 52.19493, GeoUnit.Miles, 500, Order.Ascending, GeoRadiusOptions.WithDistance)).ForAwait();
+                Assert.Equal("Member should not be a double, you likely want the GeoRadius(RedisKey, double, double, ...) overload.\r\nParameter name: member", ex.Message);
 
                 // The good stuff
                 GeoRadiusResult[] result = db.GeoRadius(key, -1.759925, 52.19493, 500, unit: GeoUnit.Miles, order: Order.Ascending, options: GeoRadiusOptions.WithDistance);
                 Assert.NotNull(result);
+
+                result = await db.GeoRadiusAsync(key, -1.759925, 52.19493, 500, unit: GeoUnit.Miles, order: Order.Ascending, options: GeoRadiusOptions.WithDistance).ForAwait();
+                Assert.NotNull(result);
             }
         }
     }

StackExchange.Redis/StackExchange/Redis/RedisDatabase.cs

@@ -216,11 +216,21 @@ private Message GetGeoRadiusMessage(RedisKey key, RedisValue? member, double lon
 
         public GeoRadiusResult[] GeoRadius(RedisKey key, RedisValue member, double radius, GeoUnit unit, int count, Order? order, GeoRadiusOptions options, CommandFlags flags)
         {
+            // This gets confused with the double overload below sometimes...throwing when this occurs.
+            if (member.Type == RedisValue.StorageType.Double)
+            {
+                throw new ArgumentException("Member should not be a double, you likely want the GeoRadius(RedisKey, double, double, ...) overload.", nameof(member));
+            }
             return ExecuteSync(GetGeoRadiusMessage(key, member, double.NaN, double.NaN, radius, unit, count, order, options, flags), ResultProcessor.GeoRadiusArray(options));
         }
 
         public Task<GeoRadiusResult[]> GeoRadiusAsync(RedisKey key, RedisValue member, double radius, GeoUnit unit, int count, Order? order, GeoRadiusOptions options, CommandFlags flags)
         {
+            // This gets confused with the double overload below sometimes...throwing when this occurs.
+            if (member.Type == RedisValue.StorageType.Double)
+            {
+                throw new ArgumentException("Member should not be a double, you likely want the GeoRadius(RedisKey, double, double, ...) overload.", nameof(member));
+            }
             return ExecuteAsync(GetGeoRadiusMessage(key, member, double.NaN, double.NaN, radius, unit, count, order, options, flags), ResultProcessor.GeoRadiusArray(options));
         }