expression.Tuple is uncomparable

[andy-wm-arthur]

expession.Tuple.Type() returns a slice of types, which cannot be compared in Golang.

tmp> create table test (pk int primary key, c0 int);
tmp> insert into test values (0,0);
Query OK, 1 row affected
tmp> delete from test where (pk,c0) = (0,0);
panic: runtime error: comparing uncomparable type sql.tupleType

goroutine 178 [running]:
github.com/dolthub/go-mysql-server/sql/expression.(*comparison).Compare(0xc00020efa0, 0xc00058db00, 0xc0002e0220, 0x2, 0x2, 0x1, 0xc0004add50, 0x1d1be9b)
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/expression/comparison.go:47 +0x27c
github.com/dolthub/go-mysql-server/sql/expression.(*Equals).Eval(0xc00020efa0, 0xc00058db00, 0xc0002e0220, 0x2, 0x2, 0x0, 0x2, 0x2, 0xc0002e0220)
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/expression/comparison.go:163 +0x5c
github.com/dolthub/go-mysql-server/sql.EvaluateCondition(0xc00058db00, 0x2851e80, 0xc00020efa0, 0xc0002e0220, 0x2, 0x2, 0xc00058a300, 0x33429a0, 0x0)
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/core.go:606 +0x62
github.com/dolthub/go-mysql-server/sql/plan.(*FilterIter).Next(0xc000369bc0, 0xc0004ade8c, 0x3, 0x2, 0x0, 0x2828780)
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/plan/filter.go:103 +0x9b
github.com/dolthub/go-mysql-server/sql/plan.(*exchangeRowIter).iterPartition(0xc00058a280, 0x28180c0, 0xc000418c70)
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/plan/exchange.go:253 +0x31d
github.com/dolthub/go-mysql-server/sql/plan.(*exchangeRowIter).start.func1(0xc00058a280, 0xc000418c60, 0x28180c0, 0xc000418c70)
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/plan/exchange.go:178 +0x3f
created by github.com/dolthub/go-mysql-server/sql/plan.(*exchangeRowIter).start
	/Users/andyarthur/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.6.1-0.20201206203230-59fe20b2e36d/sql/plan/exchange.go:177 +0x115