Now that ASTGen should be able to generate most Swift code. Let's
remove "legacy parser" call-in, and remove the unhealthy cyclic
dependency between lib/Parse and ASTGen.
* 'ASTGenVisitor' has a reference to a legacy C++ Parser configured for
ASTGen.
* If 'ASTGenVisitor' encounters a AST node that hasn't been migrated,
call parse(Decl|Stmt|Expr|Type) to parse the position using the legacy
parser.
* The legacy parser calls ASTGen's
'swift_ASTGen_build(Decl|Stmt|Expr|Type)' for each ASTNode "parsing"
(unless the call is not directly from the ASTGen.)
rdar://117151886
Merge with BasicBridging and ASTBridging
respectively. The changes here should be pretty
uncontroversial, I tried to keep it to just moving
code about.
Introduce two modes of bridging:
* inline mode: this is basically how it worked so far. Using full C++ interop which allows bridging functions to be inlined.
* pure mode: bridging functions are not inlined but compiled in a cpp file. This allows to reduce the C++ interop requirements to a minimum. No std/llvm/swift headers are imported.
This change requires a major refactoring of bridging sources. The implementation of bridging functions go to two separate files: SILBridgingImpl.h and OptimizerBridgingImpl.h.
Depending on the mode, those files are either included in the corresponding header files (inline mode), or included in the c++ file (pure mode).
The mode can be selected with the BRIDGING_MODE cmake variable. By default it is set to the inline mode (= existing behavior). The pure mode is only selected in certain configurations to work around C++ interop issues:
* In debug builds, to workaround a problem with LLDB's `po` command (rdar://115770255).
* On windows to workaround a build problem.
In code we use `#include "swift/Lib/Header.h"` which is located in
"include/swift/Lib/Header.h", so we use "include/" as a header search
path. We should put modulemaps in the same directory and shouldn't rely
on clang to search in immediate subdirectories.
rdar://106677321
