sql: panic on comparison lookup

[knz]

Found by #7409:

SELECT 89, COALESCE ( + 94, - 57, CASE 
  WHEN COUNT ( * ) NOT BETWEEN ( NULL ) AND - 43 * ( + 34 * COUNT ( * ) ) 
  THEN + ( - COALESCE ( 9, 74 ) ) 
  ELSE - MAX ( - 89 ) END
 + - COALESCE ( 80 + 11, ( + COUNT ( * ) ) ) * 95, 26 )
 + CASE NULLIF ( + 87, - 57 * SUM ( DISTINCT 42 ) ) 
     WHEN 58 THEN NULL WHEN 59 THEN NULL ELSE - 70 END AS col2;

panic: lookup for ComparisonExpr ((COUNT((*)[int]))[int] < (((NULL)[NULL]))[NULL])[bool]'s CmpOp failed                                                                                                            
goroutine 322 [running]:                                                                                                                                                                                                                                                       panic(0x15bb420, 0xc8208917b0)                                                                                                                                                                                                                                                         /mnt/kena/go1.6.2/src/runtime/panic.go:481 +0x3e6                                                                                                                                                                                                                      github.com/cockroachdb/cockroach/sql/parser.(*ComparisonExpr).memoizeFn(0xc8202e4b60)                                                                                                                                                                                                  /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/expr.go:316 +0x47d
github.com/cockroachdb/cockroach/sql/parser.NewTypedComparisonExpr(0x1, 0x7f3b424000d8, 0xc8206afd00, 0x7f3b423d2b10, 0xc8208a1940, 0xc8206afd00)                                                                                                                                      /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/expr.go:302 +0x138                                                                                                                                                                                        github.com/cockroachdb/cockroach/sql/parser.(*RangeCond).normalize(0xc8203aa690, 0xc820880e20, 0x0, 0x0)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/normalize.go:324 +0x441
github.com/cockroachdb/cockroach/sql/parser.(*normalizeVisitor).VisitPre(0xc820880e20, 0x7f3b42405328, 0xc8203aa690, 0x7f3b423d2830, 0x0, 0x0)                                                                                                                                         /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/normalize.go:369 +0xfd                                                                                                                                                                                    github.com/cockroachdb/cockroach/sql/parser.WalkExpr(0x7f3b42381d40, 0xc820880e20, 0x7f3b42405328, 0xc8203aa690, 0x0, 0x0, 0xc8203aa6e0)                                                                                                                                               /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:404 +0x56
github.com/cockroachdb/cockroach/sql/parser.(*CaseExpr).Walk(0xc8203aa6e0, 0x7f3b42381d40, 0xc820880e20, 0x0, 0x0)                                                                                                                                                                     /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:103 +0x18b
github.com/cockroachdb/cockroach/sql/parser.WalkExpr(0x7f3b42381d40, 0xc820880e20, 0x7f3b423d2830, 0xc8203aa6e0, 0x7f3b423d2830, 0xc8203aa6e0, 0x7f3b423d19f0)                                                                                                                         /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:407 +0x98
github.com/cockroachdb/cockroach/sql/parser.(*BinaryExpr).Walk(0xc82074a480, 0x7f3b42381d40, 0xc820880e20, 0x0, 0x0)                                                                                                                                                                   /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:68 +0x6d                                                                                                                                                                                          github.com/cockroachdb/cockroach/sql/parser.WalkExpr(0x7f3b42381d40, 0xc820880e20, 0x7f3b423d19f0, 0xc82074a480, 0x7f3b423d19f0, 0xc82074a480, 0xc820880e00)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:407 +0x98                                                                                                                                                                                         github.com/cockroachdb/cockroach/sql/parser.(*CoalesceExpr).Walk(0xc8203ac5c0, 0x7f3b42381d40, 0xc820880e20, 0x0, 0x0)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:147 +0xe6                                                                                                                                                                                         github.com/cockroachdb/cockroach/sql/parser.WalkExpr(0x7f3b42381d40, 0xc820880e20, 0x7f3b423d2870, 0xc8203ac5c0, 0x7f3b423d2870, 0xc8203ac5c0, 0x7f3b423d19f0)                                                                                                                         /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:407 +0x98                                                                                                                                                                                         github.com/cockroachdb/cockroach/sql/parser.(*BinaryExpr).Walk(0xc82074a580, 0x7f3b42381d40, 0xc820880e20, 0x0, 0x0)                                                                                                                                                                   /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:68 +0x6d
github.com/cockroachdb/cockroach/sql/parser.WalkExpr(0x7f3b42381d40, 0xc820880e20, 0x7f3b423d19f0, 0xc82074a580, 0x7f3b423d19f0, 0xc82074a580, 0xc82019f300)                                                                                                                           /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/walk.go:407 +0x98
github.com/cockroachdb/cockroach/sql/parser.(*Parser).NormalizeExpr(0xc820880988, 0xc8208808b0, 0x7f3b423d20a8, 0xc82074a580, 0x0, 0x0, 0x0, 0x0)                                                                                                                                      /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/parser/parse.go:129 +0x18d
github.com/cockroachdb/cockroach/sql.(*planner).analyzeExpr(0xc820880890, 0x7f3b423d19f0, 0xc8206afb80, 0xc82002ca08, 0x1, 0x1, 0xc820410270, 0x0, 0x0, 0x0, ...)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/analyze.go:1644 +0x2dd                                                                                                                                                                                           github.com/cockroachdb/cockroach/sql.(*selectNode).addRender(0xc8202ba240, 0x7f3b423d19f0, 0xc8206afb80, 0xc82072d146, 0x4, 0x0, 0x0, 0x0, 0x0)                                                                                                                                        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/select.go:635 +0x5ea                                                                                                                                                                                             github.com/cockroachdb/cockroach/sql.(*selectNode).initTargets(0xc8202ba240, 0xc8203ac480, 0x2, 0x2, 0x0, 0x0, 0x0, 0x0, 0x0)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/select.go:529 +0x156
github.com/cockroachdb/cockroach/sql.(*planner).SelectClause(0xc820880890, 0xc8206afc00, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)                                                                                                                                                  /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/select.go:309 +0x1cb
github.com/cockroachdb/cockroach/sql.(*planner).Select(0xc820880890, 0xc820410210, 0x0, 0x0, 0x0, 0x1, 0x0, 0x0, 0x0, 0x0)                                                                                                                                                             /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/select.go:254 +0x333
github.com/cockroachdb/cockroach/sql.(*planner).newPlan(0xc820880890, 0x7f3b423d0b70, 0xc820410210, 0x0, 0x0, 0x0, 0x1da9901, 0x0, 0x0, 0x0, ...)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/plan.go:273 +0x1556
github.com/cockroachdb/cockroach/sql.(*planner).makePlan(0xc820880890, 0x7f3b423d0b70, 0xc820410210, 0x817901, 0x0, 0x0, 0x0, 0x0)
        /mnt/kena/go/src/github.com/cockroachdb/cockroach/sql/plan.go:211 +0x83                                                                                                                                                                                                github.com/cockroachdb/cockroach/sql.(*Executor).execStmt(0xc8203b80f0, 0x7f3b423d0b70, 0xc820410210, 0xc820880890, 0xc820410201, 0x0, 0x0, 0x0, 0x0, 0x0, ...)