From c038268fd5b29fcb7332da74772228475e652660 Mon Sep 17 00:00:00 2001
From: Tim Holy <tim.holy@gmail.com>
Date: Tue, 19 Mar 2019 04:10:45 -0500
Subject: [PATCH] Step through invokelatest (#184)

---
 src/generate_builtins.jl | 11 ++++++-----
 src/utils.jl             |  1 +
 test/debug.jl            | 11 +++++++++++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/generate_builtins.jl b/src/generate_builtins.jl
index 0d100b9621c4c..cca634d6b8c67 100644
--- a/src/generate_builtins.jl
+++ b/src/generate_builtins.jl
@@ -131,14 +131,15 @@ function maybe_evaluate_builtin(frame, call_expr, expand::Bool)
         return Some{Any}(ntuple(i->@lookup(frame, args[i+1]), length(args)-1))
 """)
             continue
-        elseif f === Core._apply
-            # Resolve varargs calls
+        elseif f === Core._apply || f === Core._apply_latest
+            # Resolve varargs calls and invokelatest
+            fstr = scopedname(f)
             print(io,
 """
-    $head f === Core._apply
+    $head f === $fstr
         argswrapped = getargs(args, frame)
         if !expand
-            return Some{Any}(Core._apply(argswrapped...))
+            return Some{Any}($fstr(argswrapped...))
         end
         argsflat = Base.append_any((argswrapped[1],), argswrapped[2:end]...)
         new_expr = Expr(:call, map(x->isa(x, Symbol) || isa(x, Expr) || isa(x, QuoteNode) ? QuoteNode(x) : x, argsflat)...)
@@ -146,7 +147,7 @@ function maybe_evaluate_builtin(frame, call_expr, expand::Bool)
 """)
             continue
         elseif f === Core.invoke
-            print(io, 
+            print(io,
 """
     $head f === invoke
             argswrapped = getargs(args, frame)
diff --git a/src/utils.jl b/src/utils.jl
index 3bf616236008e..103c90bc6c76d 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -31,6 +31,7 @@ end
 Like `which` except it operates on the complete tuple-type `tt`.
 """
 function whichtt(@nospecialize(tt))
+    # TODO: provide explicit control over world age? In case we ever need to call "old" methods.
     m = ccall(:jl_gf_invoke_lookup, Any, (Any, UInt), tt, typemax(UInt))
     m === nothing && return nothing
     return m.func::Method
diff --git a/test/debug.jl b/test/debug.jl
index 548f9de531913..dd2d268c9dbe3 100644
--- a/test/debug.jl
+++ b/test/debug.jl
@@ -342,6 +342,17 @@ struct B{T} end
         @test get_return(frame) == f_inv(2)
     end
 
+    f_inv_latest(x::Real) = 1 + Core._apply_latest(f_inv, x)
+    @testset "invokelatest" begin
+        fr = JuliaInterpreter.enter_call(f_inv_latest, 2.0)
+        fr, pc = JuliaInterpreter.debug_command(fr, :nc)
+        frame, pc = JuliaInterpreter.debug_command(fr, :s) # step into invokelatest
+        @test frame.framecode.scope.sig == Tuple{typeof(f_inv),Real}
+        JuliaInterpreter.debug_command(frame, :c)
+        frame = root(frame)
+        @test get_return(frame) == f_inv_latest(2.0)
+    end
+
     @testset "Issue #178" begin
         remove()
         a = [1, 2, 3, 4]