Compile-Time/Syntax Error Notifications in IDE

It would be more time efficient when making a sketch to show compile-time and syntax errors while typing. Many well known IDEs support this functionality (such as MPLABX, Visual Studio, MATLAB, etc.) and it would be really nice if the Arduino IDE could support it, too.

For clarification: The Arduino IDE would display a red squiggly line underneath a line of code with a compile-time or syntax error and provide a popup note detailing the error when the user mouses over the offending line.

This way users can more efficiently debug their code without having to recompile constantly.

Is this possible?

The issue names no files, tests, or entry points; begin by reviewing the Arduino IDE 1.x editor and compilation architecture. Define the scope for live syntax and compile-time diagnostics, then identify tests that can demonstrate inline errors and hover details before implementation.

Written by the indexing model from the issue text.