[SAOC 2025] Improving D error messages Weekly Update #2

This week I focused on trying to improve the diagnostic quality of dmd by including the function or constructor name in error messages i.e. providing the logical location of errors like the C++ compiler does.

For example -

hello.cpp: In function main()

Explored the dmd error working pipeline

• Studied errors.d, specially printDiagnostic() and vreportDiagnostic(), where error messages are formatted and displayed.
• Reviewed the role of DiagnosticContext and experimented with it to carry contextual information like the current function name.
• Explored semantic3.d and funcsem.d to understand the semantic processing of function bodies.

Globals and function tracking

• Experimented with adding a currentFuncName field in globals.d for globally tracking the active function during analysis.
• Experimented with using .error() member functions on FuncDeclaration and other Dsymbol-derived classes to simplify error reporting.

Challenges / Issues Encountered

• Import cycles: Adding FuncDeclaration references in globals.d caused cyclic imports.
• Infinite recursion / silent compiler: Incorrect placement of function name tracking in semantic3() temporarily suppressed error output, likely due to recursion.

The git branch I am working on is : https://github.com/Iskaban10/dmd/tree/improve-error-msg