Concerning editors and compilers working together:

Our (Plantronics/Zehntel) UNIX-based in-circuit testers run
user-language programs which describe all the components on a board
under test and how they should be tested.  A feature of our system
is called "develop mode", which combines our screen editor with the parser
and with the interpreter which operates the testing hardware.
During debugging, test steps may be parsed *and* executed,
and the cursor is left wherever there is a syntax error or
a component measurement error, allowing the programmer to correct
the syntax error or refine the measurement values for components.
If no error arises, the results of the tests are displayed in a data window.
Debugged programs can be run flat out in a compiled "operate mode".
The editor can be run separately, too, without the parser and interpreter.
In addition, the editor knows about the data structures
of the user language, and has several features which utilize
that information.

Develop mode is an indispensable aid to test program debugging,
and is a major selling point for our test systems.  The nature of our
program execution (immediate hardware operation with display of results)
makes the addition of code execution to an editor-compiler symbiosis a natural
step, but in general the idea of tying a screen editor with a syntax
checker (Unix pipes make this easy) is a real winner which I would like
to see incorporated into the design of new editors.