bug#345: Bug in F90 mode

[Gabor Toth <GTOTH@UMICH.EDU>]

Dear GNU emacs developers,

I truly appreciate the work put into the emacs editor. This is the  
editor of choice for editing source code files because of the many  
advanced features that help programmers. I have been using the F90  
module for a long time and I encountered a small but annoying bug. I  
tried to work around it, but I could not.

The bug is present in every version of emacs I know of. It is a bug  
in the F90 module. To reproduced the bug, simply create a file  
with .f90 extension, say

bug.f90

open the file, and type the following lines

program bug

    AnyVariable = 1.0
    TypeVariable = 2.0
        OtherVariable = 3.0

    end program bug

and let Emacs indent it (by hitting TAB at the beginning of each  
line). The result is what you see above, ie the lines following the  
TypeVariable = 2.0 line are indented.

The reason is that if a line starts withTypeXXX the F90 module  
regards it as a type definition, although it is not matched when an  
end statement is typed. I suspect that the error is in the definition  
of f90-type-def-re in the f90.el file. The definition is

(defconst f90-type-def-re
   "\\<\\(type\\)\\([^(\n]*\\)\\(::\\)?[ \t]*\\b\\(\\sw+\\)")

It seems that this regular expression is too permissive. The [^(\n]**  
part matches anything that follows the "type" string except for  
opening paren and end-of-line. This should probably be replaced with  
[ \t]*

I would be greatful if you could suggest a work around that I can put  
into my .emacs file. My attempts at redefining the f90-type-def-re  
did not work. I managed to set the indentation to 0 for type/ 
interface/blockdata definitions to avoid this problem, but then the  
true type and interface definitions will not be indented, and that's  
pretty ugly. We have some huge F90 codes, and not allowing variables  
to start with the string "type" is not an option.

Thanks for your work and kind help,

Gabor Toth
Research scientist
University of Michigan