Main API for compiling plain Haskell source code.

This module implements compilation of a Haskell source. It is not concerned with preprocessing of source files; this is handled in DriverPipeline.

There are various entry points depending on what mode we're in: "batch" mode (--make), "one-shot" mode (-c, -S etc.), and "interactive" mode (GHCi). There are also entry points for individual passes: parsing, typechecking/renaming, desugaring, and simplification.

All the functions here take an HscEnv as a parameter, but none of them return a new one: HscEnv is treated as an immutable value from here on in (although it has mutable components, for the caches).

Warning messages are dealt with consistently throughout this API: during compilation warnings are collected, and before any function in HscMain returns, the warnings are either printed, or turned into a real compialtion error if the -Werror flag is enabled.

(c) The GRASP/AQUA Project, Glasgow University, 1993-2000