Confusing parse errors for bad array specs

[tskeith]

Test program:

subroutine s(x)
  real :: x(10,:)
end

Compiler output:

a.f90:6:8: error: expected '('
    real :: x(10,:)
         ^
a.f90:6:3: in the context: statement function definition
    real :: x(10,:)
    ^
a.f90:6:3: in the context: declaration construct
a.f90:6:3: in the context: specification part
a.f90:5:1: in the context: SUBROUTINE subprogram
  subroutine s(x)
  ^

In this case the user has combined valid shape-specs (10 and :) in a way that makes an invalid array-spec. But the error messages aren't very helpful to figure that out.

Here are some other examples that get a similar error message:

real :: x(*,10)
real :: x(10,..)
real :: x(:,*)

One fix would be for the parser to accept any sequence of shape-specs and then leave it to semantics to report bad combinations. We already have to detect valid array-specs that are used in the wrong context.

[klausler]

Another approach to a fix would be to perform custom error recovery on array-specs, and just accept any list of token sequences with properly nested parentheses.