Merge pull request #54 from JuliaLang/cjf/core-set-parser

Minor cleanups to core parser hook

Author: c42f

src/hooks.jl

@@ -1,42 +1,42 @@
 # This file provides an adaptor to match the API expected by the Julia runtime
 # code in the binding Core._parse
 
-function _set_core_parse_hook(parser)
-    # HACK! Fool the runtime into allowing us to set Core._parse, even during
-    # incremental compilation. (Ideally we'd just arrange for Core._parse to be
-    # set to the JuliaSyntax parser. But how do we signal that to the dumping
-    # code outside of the initial creation of Core?)
-    i = findfirst(==(:incremental), fieldnames(Base.JLOptions))
-    ptr = convert(Ptr{fieldtype(Base.JLOptions, i)},
-                  cglobal(:jl_options, Base.JLOptions) + fieldoffset(Base.JLOptions, i))
-    incremental = unsafe_load(ptr)
-    if incremental != 0
-        unsafe_store!(ptr, 0)
-    end
+if isdefined(Core, :set_parser)
+    const _set_core_parse_hook = Core.set_parser
+else
+    function _set_core_parse_hook(parser)
+        # HACK! Fool the runtime into allowing us to set Core._parse, even during
+        # incremental compilation. (Ideally we'd just arrange for Core._parse to be
+        # set to the JuliaSyntax parser. But how do we signal that to the dumping
+        # code outside of the initial creation of Core?)
+        i = findfirst(==(:incremental), fieldnames(Base.JLOptions))
+        ptr = convert(Ptr{fieldtype(Base.JLOptions, i)},
+                      cglobal(:jl_options, Base.JLOptions) + fieldoffset(Base.JLOptions, i))
+        incremental = unsafe_load(ptr)
+        if incremental != 0
+            unsafe_store!(ptr, 0)
+        end
 
-    Base.eval(Core, :(_parse = $parser))
+        Base.eval(Core, :(_parse = $parser))
 
-    if incremental != 0
-        unsafe_store!(ptr, incremental)
+        if incremental != 0
+            unsafe_store!(ptr, incremental)
+        end
     end
 end
 
 # Use caller's world age.
-const _caller_world = typemax(UInt)
-const _parser_world_age = Ref{UInt}(_caller_world)
+const _latest_world = typemax(UInt)
+const _parser_world_age = Ref{UInt}(_latest_world)
 
 function core_parser_hook(code, filename, lineno, offset, options)
-    # `hook` is always _core_parser_hook, but that's hidden from the compiler
-    # via a Ref to prevent invalidation / recompilation when other packages are
-    # loaded. This wouldn't seem like it should be necessary given the use of
-    # invoke_in_world, but it is in Julia-1.7.3. I'm not sure exactly which
-    # latency it's removing.
-    hook = _core_parser_hook_ref[]
-    if _parser_world_age[] != _caller_world
-        Base.invoke_in_world(_parser_world_age[], hook,
+    # NB: We need an inference barrier of one type or another here to prevent
+    # invalidations. The invokes provide this currently.
+    if _parser_world_age[] != _latest_world
+        Base.invoke_in_world(_parser_world_age[], _core_parser_hook,
                              code, filename, lineno, offset, options)
     else
-        hook(code, filename, lineno, offset, options)
+        Base.invokelatest(_core_parser_hook, code, filename, lineno, offset, options)
     end
 end
 
@@ -146,8 +146,6 @@ end
 Base.Meta.ParseError(e::JuliaSyntax.ParseError) = e
 
 const _default_parser = Core._parse
-# NB: Never reassigned, but the compiler doesn't know this!
-const _core_parser_hook_ref = Ref{Function}(_core_parser_hook)
 
 """
     enable_in_core!([enable=true; freeze_world_age, debug_filename])
@@ -165,7 +163,7 @@ Keyword arguments:
 """
 function enable_in_core!(enable=true; freeze_world_age = true,
         debug_filename   = get(ENV, "JULIA_SYNTAX_DEBUG_FILE", nothing))
-    _parser_world_age[] = freeze_world_age ? Base.get_world_counter() : _caller_world
+    _parser_world_age[] = freeze_world_age ? Base.get_world_counter() : _latest_world
     if enable && !isnothing(debug_filename)
         _debug_log[] = open(debug_filename, "w")
     elseif !enable && !isnothing(_debug_log[])