Why Lazarus needs Free Pascal sources?

[geek893]

Lazarus says that they are required "for browsing and code completion", but I don't understand what it means.

What functions are unavailable if FP source codes aren't installed?

[Bart]

CodeTools need the fpc source.

Bart

[Ñuño_Martínez]

What functions are unavailable if FP source codes aren't installed?

Lazarus won't be able to do an in-deep debugging of your code, code completion will not wok at full power, and some other helper functions whould be affected.

Read this for more information about the Lazarus IDE tools.

[Zoran]

Lazarus says that they are required "for browsing and code completion", but I don't understand what it means.

What functions are unavailable if FP source codes aren't installed?

Code completion will not work means that when you start typing the function name in your code, you will not get the complete function name offered by the source editor. All functions will still work, though.

[Graeme]

Code completion will not work means that when you start typing the function name in your code, you will not get the complete function name offered by the source editor.

If that is the case, it can be inaccurate and improved to not require FPC source code. Let me explain.

Inaccurate:
  If it uses the source code to determine function names and properties,
  and you are using FPC Trunk code, but a slightly older FPC Trunk
  binary, the source code could show a function or property, but that
  isn't already in the current FPC Trunk binary.

Not requiring FPC source code:
  CodeTools could be improved to actually read the compiled .PPU files
  directly. FPC already includes a console utility to show how to do this.
  This also means that CodeTools will not have the previous issue
  mentioned. The FPC binary selected and the related .PPU files will
  always match and give a true view of what methods or properties
  are available when you hit Compile.

The other point is that not requiring FPC source code, means you will save a lot of disk space - that could be very important for certain platforms.