Type mismatch error for map and var assignments reports a different location

[lenticularis39]

Assignment of an incorrect type to a map is reported at the location of the map expression, while an assignment of an incorrect type to a variable is reported at the location of the entire assignment statement:

# bpftrace -e 'BEGIN { @a = ""; @a = 1; }'
stdin:1:18-20: ERROR: Type mismatch for @a: trying to assign value of type 'int64' when map already contains a value of type 'string[1]
BEGIN { @a = ""; @a = 1; }
                 ~~
# bpftrace -e 'BEGIN { $a = ""; $a = 1; }'
stdin:1:18-24: ERROR: Type mismatch for $a: trying to assign value of type 'int64' when variable already contains a value of type 'string[1]'
BEGIN { $a = ""; $a = 1; }
                 ~~~~~~

Ideally, the reported location of the error should be consistent between these two cases.

[danobi]

Makes sense. I think the latter (scratch variable) diagnostic is better