Defining ranges by more than 2 cells.

Description

=SUM(B4:B5:C5) should be equal to =SUM(B4:C5)

According to OpenFormula article 6.4.11 standard:

6.4.11 Infix Operator

Reference Range (":")
Summary: Computes an inclusive range given two references
Syntax: Reference Left : Reference Right
Returns: Reference
Constraints: None

Semantics: Takes two references and computes the range, that is, a reference to the smallest 3-dimensional cube of cells that include both Left and Right including the cells on sheets positioned between Left and Right. Left and Right need not be a single cell. For an expression such as [.B4:.B5]:[.C5] the resulting range is B4:C5. In case Left and/or Right involve a reference list (result of operator reference union), the range is computed and extended for each element of the list(s).

Note: For example, (a,b,c,d denoting one reference each) (a~ b):(c~d) computes a: b:c:d determining the outermost front-top-left and rear-bottom-right corners.

Left and Right may also be defined names or the result of a function returning a reference, such as INDIRECT.

Links

#832
#834

Start by reproducing the formula comparison in the issue and read the linked issues #832 and #834 for related context. Trace how the reference-range operator handles B4:B5:C5; done means =SUM(B4:B5:C5) evaluates the same as =SUM(B4:C5) in line with the cited OpenFormula semantics.