quality improvement for recompile_invalidations (#36)

* quality improvement for recompile_invalidations

The previous implementation was unnecessarily forcing compilation of the wrapper code for each use of the macro, and was assuming that hygiene rules do not apply to a gensym in a toplevel block and assuming that the internal tryfinally syntax is legal to generate directly. This change tries to avoid all of those assumptions, and should therefore also give better backtraces too.

* Update invalidations.jl

src/invalidations.jl

@@ -8,17 +8,21 @@ Recompile any invalidations that occur within the given expression. This is gene
 by users in creating "Startup" packages to ensure that the code compiled by package authors is not invalidated.
 """
 macro recompile_invalidations(expr)
-    list = gensym(:list)
-    Expr(:toplevel,
-        :($list = ccall(:jl_debug_method_invalidation, Any, (Cint,), 1)),
-        Expr(:tryfinally,
-            esc(expr),
-            :(ccall(:jl_debug_method_invalidation, Any, (Cint,), 0))
-        ),
-        :(if ccall(:jl_generating_output, Cint, ()) == 1
-            foreach($PrecompileTools.precompile_mi, $PrecompileTools.invalidation_leaves($list))
-          end)
-    )
+    # use QuoteNode instead of esc(Expr(:quote)) so that $ is not permitted as usual (instead of having this macro work like `@eval`)
+    return :(recompile_invalidations($__module__, $(QuoteNode(expr))))
+end
+
+function recompile_invalidations(__module__::Module, @nospecialize expr)
+    list = ccall(:jl_debug_method_invalidation, Any, (Cint,), 1)
+    try
+        Core.eval(__module__, expr)
+    finally
+        ccall(:jl_debug_method_invalidation, Any, (Cint,), 0)
+    end
+    if ccall(:jl_generating_output, Cint, ()) == 1
+        foreach(precompile_mi, invalidation_leaves(list))
+    end
+    nothing
 end
 
 function invalidation_leaves(invlist)