## What changes were proposed in this pull request?
Currently we find the wider common type by comparing the two types from left to right, this can be a problem when you have two data types which don't have a common type but each can be promoted to StringType.
For instance, if you have a table with the schema:
[c1: date, c2: string, c3: int]
The following succeeds:
SELECT coalesce(c1, c2, c3) FROM table
While the following produces an exception:
SELECT coalesce(c1, c3, c2) FROM table
This is only a issue when the seq of dataTypes contains `StringType` and all the types can do string promotion.
close#19033
## How was this patch tested?
Add test in `TypeCoercionSuite`
Author: Xingbo Jiang <xingbo.jiang@databricks.com>
Closes#21074 from jiangxb1987/typeCoercion.
d96c3e33cc