From 013fe08d9993dcd6758add3707ecddeddd7b26ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Fri, 18 Apr 2025 11:18:01 -0400
Subject: [PATCH 01/16] Parametrize signatures by method table

---
 Project.toml            |  2 +-
 src/LoweredCodeUtils.jl |  2 +-
 src/signatures.jl       | 27 +++++++++++++++------------
 test/signatures.jl      | 21 ++++++++++++---------
 4 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/Project.toml b/Project.toml
index a9616c2..b4d500b 100644
--- a/Project.toml
+++ b/Project.toml
@@ -7,7 +7,7 @@ version = "3.1.0"
 JuliaInterpreter = "aa1ae85d-cabe-5617-a682-6adf51b2e16a"
 
 [compat]
-JuliaInterpreter = "0.9"
+JuliaInterpreter = "0.9.45"
 julia = "1.10"
 
 [extras]
diff --git a/src/LoweredCodeUtils.jl b/src/LoweredCodeUtils.jl
index bdeb7de..b166205 100644
--- a/src/LoweredCodeUtils.jl
+++ b/src/LoweredCodeUtils.jl
@@ -13,7 +13,7 @@ using JuliaInterpreter
 using JuliaInterpreter: SSAValue, SlotNumber, Frame
 using JuliaInterpreter: @lookup, moduleof, pc_expr, step_expr!, is_global_ref, is_quotenode_egal, whichtt,
                         next_until!, finish_and_return!, get_return, nstatements, codelocation, linetable,
-                        is_return, lookup_return
+                        is_return, lookup_return, extract_method_table
 
 include("packagedef.jl")
 
diff --git a/src/signatures.jl b/src/signatures.jl
index 2e77c8e..c744b66 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -53,9 +53,10 @@ function signature(@nospecialize(recurse), frame::Frame, @nospecialize(stmt), pc
         stmt = pc_expr(frame, pc)
     end
     isa(stmt, Expr) || return nothing, pc
+    mt = extract_method_table(frame, stmt; eval = false)
     sigsv = @lookup(frame, stmt.args[2])::SimpleVector
     sigt = signature(sigsv)
-    return sigt, lastpc
+    return mt => sigt, lastpc
 end
 signature(@nospecialize(recurse), frame::Frame, pc) = signature(recurse, frame, pc_expr(frame, pc), pc)
 signature(frame::Frame, pc) = signature(finish_and_return!, frame, pc)
@@ -439,9 +440,9 @@ function get_running_name(@nospecialize(recurse), frame, pc, name, parentname)
         pctop -= 1
         stmt = pc_expr(frame, pctop)
     end   # end fix
-    sigtparent, lastpcparent = signature(recurse, frame, pctop)
+    (mt, sigtparent), lastpcparent = signature(recurse, frame, pctop)
     sigtparent === nothing && return name, pc, lastpcparent
-    methparent = whichtt(sigtparent)
+    methparent = whichtt(sigtparent, mt)
     methparent === nothing && return name, pc, lastpcparent  # caller isn't defined, no correction is needed
     if isgen
         cname = GlobalRef(moduleof(frame), nameof(methparent.generator.gen))
@@ -507,6 +508,8 @@ function skip_until!(predicate, @nospecialize(recurse), frame)
     return pc
 end
 
+method_table(method::Method) = isdefined(method, :external_mt) ? method.external_mt::MethodTable : nothing
+
 """
     ret = methoddef!(recurse, signatures, frame; define=true)
     ret = methoddef!(signatures, frame; define=true)
@@ -536,22 +539,22 @@ function methoddef!(@nospecialize(recurse), signatures, frame::Frame, @nospecial
     if ismethod3(stmt)
         pc3 = pc
         arg1 = stmt.args[1]
-        sigt, pc = signature(recurse, frame, stmt, pc)
-        meth = whichtt(sigt)
+        (mt, sigt), pc = signature(recurse, frame, stmt, pc)
+        meth = whichtt(sigt, mt)
         if isa(meth, Method) && (meth.sig <: sigt && sigt <: meth.sig)
             pc = define ? step_expr!(recurse, frame, stmt, true) : next_or_nothing!(recurse, frame)
         elseif define
             pc = step_expr!(recurse, frame, stmt, true)
-            meth = whichtt(sigt)
+            meth = whichtt(sigt, mt)
         end
         if isa(meth, Method) && (meth.sig <: sigt && sigt <: meth.sig)
-            push!(signatures, meth.sig)
+            push!(signatures, mt => meth.sig)
         else
             if arg1 === false || arg1 === nothing
                 # If it's anonymous and not defined, define it
                 pc = step_expr!(recurse, frame, stmt, true)
-                meth = whichtt(sigt)
-                isa(meth, Method) && push!(signatures, meth.sig)
+                meth = whichtt(sigt, mt)
+                isa(meth, Method) && push!(signatures, mt => meth.sig)
                 return pc, pc3
             else
                 # guard against busted lookup, e.g., https://github.com/JuliaLang/julia/issues/31112
@@ -592,7 +595,7 @@ function methoddef!(@nospecialize(recurse), signatures, frame::Frame, @nospecial
     end
     found || return nothing
     while true  # methods containing inner methods may need multiple trips through this loop
-        sigt, pc = signature(recurse, frame, stmt, pc)
+        (mt, sigt), pc = signature(recurse, frame, stmt, pc)
         stmt = pc_expr(frame, pc)
         while !isexpr(stmt, :method, 3)
             pc = next_or_nothing(recurse, frame, pc)  # this should not check define, we've probably already done this once
@@ -607,8 +610,8 @@ function methoddef!(@nospecialize(recurse), signatures, frame::Frame, @nospecial
         # signature of the active method. So let's get the active signature.
         frame.pc = pc
         pc = define ? step_expr!(recurse, frame, stmt, true) : next_or_nothing!(recurse, frame)
-        meth = whichtt(sigt)
-        isa(meth, Method) && push!(signatures, meth.sig) # inner methods are not visible
+        meth = whichtt(sigt, mt)
+        isa(meth, Method) && push!(signatures, mt => meth.sig) # inner methods are not visible
         name === name3 && return pc, pc3     # if this was an inner method we should keep going
         stmt = pc_expr(frame, pc)  # there *should* be more statements in this frame
     end
diff --git a/test/signatures.jl b/test/signatures.jl
index 8adb2b8..cf197b4 100644
--- a/test/signatures.jl
+++ b/test/signatures.jl
@@ -97,7 +97,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
 
     # Manually add the signature for the Caller constructor, since that was defined
     # outside of manual lowering
-    push!(signatures, Tuple{Type{Lowering.Caller}})
+    push!(signatures, nothing => Tuple{Type{Lowering.Caller}})
 
     nms = names(Lowering; all=true)
     modeval, modinclude = getfield(Lowering, :eval), getfield(Lowering, :include)
@@ -107,7 +107,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
         isa(f, Base.Callable) || continue
         (f === modeval || f === modinclude) && continue
         for m in methods(f)
-            if m.sig ∉ signatures
+            if (nothing => m.sig) ∉ signatures
                 push!(failed, m.sig)
             end
         end
@@ -151,7 +151,8 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     rename_framemethods!(frame)
     methoddefs!(signatures, frame; define=false)
     @test length(signatures) == 1
-    @test LoweredCodeUtils.whichtt(signatures[1]) == first(methods(Lowering.fouter))
+    mt, sig = first(signatures)
+    @test LoweredCodeUtils.whichtt(sig, mt) == first(methods(Lowering.fouter))
 
     # Check output of methoddef!
     frame = Frame(Lowering, :(function nomethod end))
@@ -170,7 +171,8 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     signatures = Set{Any}()
     methoddef!(signatures, frame; define=false)
     @test length(signatures) == 1
-    @test first(signatures) == which(Base.max_values, Tuple{Type{Int16}}).sig
+    mt, sig = first(signatures)
+    @test sig == which(Base.max_values, Tuple{Type{Int16}}).sig
 
     # define
     ex = :(fdefine(x) = 1)
@@ -291,7 +293,8 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     JuliaInterpreter.next_until!(LoweredCodeUtils.ismethod3, frame, true)
     empty!(signatures)
     methoddefs!(signatures, frame; define=true)
-    @test first(signatures).parameters[end] == Int
+    mt, sig = first(signatures)
+    @test sig.parameters[end] == Int
 
     # Multiple keyword arg methods per frame
     # (Revise issue #363)
@@ -310,7 +313,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     @test kw2sig ∉ signatures
     pc = methoddefs!(signatures, frame; define=false)
     @test pc === nothing
-    @test kw2sig ∈ signatures
+    @test (nothing => kw2sig) ∈ signatures
 
     # Module-scoping
     ex = :(Base.@irrational π        3.14159265358979323846  pi)
@@ -336,7 +339,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     rename_framemethods!(frame)
     empty!(signatures)
     methoddefs!(signatures, frame; define=false)
-    @test Tuple{typeof(Lowering.CustomMS)} ∈ signatures
+    @test (nothing => Tuple{typeof(Lowering.CustomMS)}) ∈ signatures
 
     # https://github.com/timholy/Revise.jl/issues/398
     ex = quote
@@ -370,7 +373,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     frame = Frame(Lowering422, ex)
     rename_framemethods!(frame)
     pc = methoddefs!(signatures, frame; define=false)
-    @test typeof(Lowering422.fneg) ∈ Set(Base.unwrap_unionall(sig).parameters[1] for sig in signatures)
+    @test typeof(Lowering422.fneg) ∈ Set(Base.unwrap_unionall(sig).parameters[1] for (mt, sig) in signatures)
 
     # Scoped names (https://github.com/timholy/Revise.jl/issues/568)
     ex = :(f568() = -1)
@@ -385,7 +388,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
         pc = JuliaInterpreter.step_expr!(finish_and_return!, frame, true)
     end
     pc = methoddef!(finish_and_return!, signatures, frame, pc; define=true)
-    @test Tuple{typeof(Lowering.f568)} ∈ signatures
+    @test (nothing => Tuple{typeof(Lowering.f568)}) ∈ signatures
     @test Lowering.f568() == -2
 
     # Undefined names

From 4610b4bf6f3b884b0192ed570c43713e65ff70e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Fri, 18 Apr 2025 11:18:21 -0400
Subject: [PATCH 02/16] Add tests

---
 test/signatures.jl | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/test/signatures.jl b/test/signatures.jl
index cf197b4..5fa7132 100644
--- a/test/signatures.jl
+++ b/test/signatures.jl
@@ -505,4 +505,26 @@ end
 
 end
 
+@testset "Support for external method tables" begin
+    ExternalMT = Module()
+    Core.eval(ExternalMT, :(Base.Experimental.@MethodTable method_table))
+    signatures = []
+
+    ex = :(Base.sin(::Float64) = "sin")
+    Core.eval(ExternalMT, ex)
+    frame = Frame(ExternalMT, ex)
+    pc = methoddefs!(signatures, frame; define = false)
+    @test length(signatures) == 1
+    (mt, sig) = pop!(signatures)
+    @test (mt, sig) === (nothing, Tuple{typeof(sin), Float64})
+
+    ex = :(Base.Experimental.@overlay method_table sin(::Float64) = "sin")
+    Core.eval(ExternalMT, ex)
+    frame = Frame(ExternalMT, ex)
+    pc = methoddefs!(signatures, frame; define = false)
+    @test length(signatures) == 1
+    (mt, sig) = pop!(signatures)
+    @test (mt, sig) === (ExternalMT.method_table, Tuple{typeof(sin), Float64})
+end
+
 end # module signatures

From f53718b889bd3b0805ddced318b2dace3957e1f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.bel@hotmail.fr>
Date: Mon, 21 Apr 2025 17:21:09 +0200
Subject: [PATCH 03/16] Update src/signatures.jl

Co-authored-by: Shuhei Kadowaki <40514306+aviatesk@users.noreply.github.com>
---
 src/signatures.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/signatures.jl b/src/signatures.jl
index c744b66..937f618 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -56,7 +56,7 @@ function signature(@nospecialize(recurse), frame::Frame, @nospecialize(stmt), pc
     mt = extract_method_table(frame, stmt; eval = false)
     sigsv = @lookup(frame, stmt.args[2])::SimpleVector
     sigt = signature(sigsv)
-    return mt => sigt, lastpc
+    return Pair{Union{Nothing,MethodTable},Any}(mt, sigt), lastpc
 end
 signature(@nospecialize(recurse), frame::Frame, pc) = signature(recurse, frame, pc_expr(frame, pc), pc)
 signature(frame::Frame, pc) = signature(finish_and_return!, frame, pc)

From 6ee24af055ae9f6e4aab1ace59af290cca9bdbe6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 11:21:34 -0400
Subject: [PATCH 04/16] Update docstring

---
 src/signatures.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/signatures.jl b/src/signatures.jl
index c744b66..a84dbc1 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -514,8 +514,8 @@ method_table(method::Method) = isdefined(method, :external_mt) ? method.external
     ret = methoddef!(recurse, signatures, frame; define=true)
     ret = methoddef!(signatures, frame; define=true)
 
-Compute the signature of a method definition. `frame.pc` should point to a
-`:method` expression. Upon exit, the new signature will be added to `signatures`.
+Compute the method table/signature pair of a method definition. `frame.pc` should point to a
+`:method` expression. Upon exit, the new method table/signature pair will be added to `signatures`.
 
 There are several possible return values:
 

From 1ecbfcf5d2a1fbc8e389f92173f05ecc558d1e6b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 11:22:11 -0400
Subject: [PATCH 05/16] Tighten the type of `signatures`

---
 src/signatures.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/signatures.jl b/src/signatures.jl
index a84dbc1..1f9915e 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -534,7 +534,7 @@ occurs for "empty method" expressions, e.g., `:(function foo end)`. `pc` will be
 By default the method will be defined (evaluated). You can prevent this by setting `define=false`.
 This is recommended if you are simply extracting signatures from code that has already been evaluated.
 """
-function methoddef!(@nospecialize(recurse), signatures, frame::Frame, @nospecialize(stmt), pc::Int; define::Bool=true)
+function methoddef!(@nospecialize(recurse), signatures::Vector{Pair{Union{Nothing,MethodTable},Any}}, frame::Frame, @nospecialize(stmt), pc::Int; define::Bool=true)
     framecode, pcin = frame.framecode, pc
     if ismethod3(stmt)
         pc3 = pc

From 80581f0886170b057b4dc3fb94d5e224be934898 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 13:00:57 -0400
Subject: [PATCH 06/16] Use MethodInfoKey from CodeTracking

---
 src/LoweredCodeUtils.jl | 2 ++
 src/packagedef.jl       | 2 +-
 src/signatures.jl       | 4 ++--
 test/signatures.jl      | 9 +++++----
 4 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/LoweredCodeUtils.jl b/src/LoweredCodeUtils.jl
index 78b3210..629981e 100644
--- a/src/LoweredCodeUtils.jl
+++ b/src/LoweredCodeUtils.jl
@@ -9,6 +9,8 @@ module LoweredCodeUtils
 # This somewhat unusual structure is in place to support
 # the VS Code extension integration.
 
+using CodeTracking: MethodInfoKey
+
 using JuliaInterpreter
 using JuliaInterpreter: SSAValue, SlotNumber, Frame
 using JuliaInterpreter: @lookup, moduleof, pc_expr, step_expr!, is_global_ref, is_global_ref_egal, is_quotenode_egal, whichtt,
diff --git a/src/packagedef.jl b/src/packagedef.jl
index b25c166..c99cedd 100644
--- a/src/packagedef.jl
+++ b/src/packagedef.jl
@@ -1,6 +1,6 @@
 Base.Experimental.@optlevel 1
 
-using Core: SimpleVector, MethodTable
+using Core: SimpleVector
 using Core.IR: CodeInfo, GotoIfNot, GotoNode, IR, MethodInstance, ReturnNode
 @static if isdefined(Core.IR, :EnterNode)
     using Core.IR: EnterNode
diff --git a/src/signatures.jl b/src/signatures.jl
index 2cc70b5..8b7a5bd 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -56,7 +56,7 @@ function signature(@nospecialize(recurse), frame::Frame, @nospecialize(stmt), pc
     mt = extract_method_table(frame, stmt; eval = false)
     sigsv = @lookup(frame, stmt.args[2])::SimpleVector
     sigt = signature(sigsv)
-    return Pair{Union{Nothing,MethodTable},Any}(mt, sigt), lastpc
+    return MethodInfoKey(mt, sigt), lastpc
 end
 signature(@nospecialize(recurse), frame::Frame, pc) = signature(recurse, frame, pc_expr(frame, pc), pc)
 signature(frame::Frame, pc) = signature(finish_and_return!, frame, pc)
@@ -534,7 +534,7 @@ occurs for "empty method" expressions, e.g., `:(function foo end)`. `pc` will be
 By default the method will be defined (evaluated). You can prevent this by setting `define=false`.
 This is recommended if you are simply extracting signatures from code that has already been evaluated.
 """
-function methoddef!(@nospecialize(recurse), signatures::Vector{Pair{Union{Nothing,MethodTable},Any}}, frame::Frame, @nospecialize(stmt), pc::Int; define::Bool=true)
+function methoddef!(@nospecialize(recurse), signatures::Vector{MethodInfoKey}, frame::Frame, @nospecialize(stmt), pc::Int; define::Bool=true)
     framecode, pcin = frame.framecode, pc
     if ismethod3(stmt)
         pc3 = pc
diff --git a/test/signatures.jl b/test/signatures.jl
index 5ddd0b9..91606c4 100644
--- a/test/signatures.jl
+++ b/test/signatures.jl
@@ -2,6 +2,7 @@ module Signatures
 
 using LoweredCodeUtils
 using InteractiveUtils
+using CodeTracking: MethodInfoKey
 using JuliaInterpreter
 using JuliaInterpreter: finish_and_return!
 using Core: CodeInfo
@@ -34,7 +35,7 @@ bodymethtest4(x, y=1) = 4
 bodymethtest5(x, y=Dict(1=>2)) = 5
 
 @testset "Signatures" begin
-    signatures = Set{Any}()
+    signatures = MethodInfoKey[]
     newcode = CodeInfo[]
     for ex in (:(f(x::Int8; y=0) = y),
                :(f(x::Int16; y::Int=0) = 2),
@@ -139,7 +140,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     @test g(3) == 6
 
     # Don't be deceived by inner methods
-    signatures = []
+    signatures = MethodInfoKey[]
     ex = quote
         function fouter(x)
             finner(::Float16) = 2x
@@ -168,7 +169,7 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     ex = :(max_values(T::Union{map(X -> Type{X}, Base.BitIntegerSmall_types)...}) = 1 << (8*sizeof(T)))  # base/abstractset.jl
     frame = Frame(Base, ex)
     rename_framemethods!(frame)
-    signatures = Set{Any}()
+    signatures = MethodInfoKey[]
     methoddef!(signatures, frame; define=false)
     @test length(signatures) == 1
     mt, sig = first(signatures)
@@ -507,7 +508,7 @@ end
 @testset "Support for external method tables" begin
     ExternalMT = Module()
     Core.eval(ExternalMT, :(Base.Experimental.@MethodTable method_table))
-    signatures = []
+    signatures = MethodInfoKey[]
 
     ex = :(Base.sin(::Float64) = "sin")
     Core.eval(ExternalMT, ex)

From 1910570e86c5c6311fa883f1ef284b5384b5b87d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 13:41:56 -0400
Subject: [PATCH 07/16] Add CodeTracking as a direct dependency

---
 Project.toml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Project.toml b/Project.toml
index 5e80544..3e7625f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -4,9 +4,11 @@ authors = ["Tim Holy <tim.holy@gmail.com>"]
 version = "3.2.1"
 
 [deps]
+CodeTracking = "da1fd8a2-8d9e-5ec2-8556-3022fb5608a2"
 JuliaInterpreter = "aa1ae85d-cabe-5617-a682-6adf51b2e16a"
 
 [compat]
+CodeTracking = "2"
 JuliaInterpreter = "0.9.45"
 julia = "1.10"
 

From 118978ae80e6b50caf308ff0543d72327bfa784e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 13:42:49 -0400
Subject: [PATCH 08/16] Remove `method_table` definition

We already used `extract_method_table` from JuliaInterpreter, obsoleting the introduction
of `method_table`.
---
 src/signatures.jl | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/signatures.jl b/src/signatures.jl
index 8b7a5bd..e533158 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -508,8 +508,6 @@ function skip_until!(predicate, @nospecialize(recurse), frame)
     return pc
 end
 
-method_table(method::Method) = isdefined(method, :external_mt) ? method.external_mt::MethodTable : nothing
-
 """
     ret = methoddef!(recurse, signatures, frame; define=true)
     ret = methoddef!(signatures, frame; define=true)

From d8bd0bd5703fe36c5258a8bac1cf3425279f9365 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 13:43:26 -0400
Subject: [PATCH 09/16] Don't accidentally override `Base.sin(::Float64)`

---
 test/signatures.jl | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/test/signatures.jl b/test/signatures.jl
index 91606c4..dce60ce 100644
--- a/test/signatures.jl
+++ b/test/signatures.jl
@@ -510,21 +510,21 @@ end
     Core.eval(ExternalMT, :(Base.Experimental.@MethodTable method_table))
     signatures = MethodInfoKey[]
 
-    ex = :(Base.sin(::Float64) = "sin")
+    ex = :(foo(x) = "foo")
     Core.eval(ExternalMT, ex)
     frame = Frame(ExternalMT, ex)
     pc = methoddefs!(signatures, frame; define = false)
     @test length(signatures) == 1
     (mt, sig) = pop!(signatures)
-    @test (mt, sig) === (nothing, Tuple{typeof(sin), Float64})
+    @test (mt, sig) === (nothing, Tuple{typeof(ExternalMT.foo), Any})
 
-    ex = :(Base.Experimental.@overlay method_table sin(::Float64) = "sin")
+    ex = :(Base.Experimental.@overlay method_table foo(x) = "overlayed foo")
     Core.eval(ExternalMT, ex)
     frame = Frame(ExternalMT, ex)
     pc = methoddefs!(signatures, frame; define = false)
     @test length(signatures) == 1
     (mt, sig) = pop!(signatures)
-    @test (mt, sig) === (ExternalMT.method_table, Tuple{typeof(sin), Float64})
+    @test (mt, sig) === (ExternalMT.method_table, Tuple{typeof(ExternalMT.foo), Any})
 end
 
 end # module signatures

From 73d89d5741d822e9d564255d83432a24c05813eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 13:46:27 -0400
Subject: [PATCH 10/16] Temporarily add CodeTracking PR for CI testing

---
 .github/workflows/CI.yml         | 1 +
 .github/workflows/Documenter.yml | 1 +
 2 files changed, 2 insertions(+)

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 811de4d..ed696af 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -54,6 +54,7 @@ jobs:
             ${{ runner.os }}-test-${{ env.cache-name }}-
             ${{ runner.os }}-test-
             ${{ runner.os }}-
+      - run: julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
       - uses: julia-actions/julia-processcoverage@v1
diff --git a/.github/workflows/Documenter.yml b/.github/workflows/Documenter.yml
index b91b123..6b0146a 100644
--- a/.github/workflows/Documenter.yml
+++ b/.github/workflows/Documenter.yml
@@ -11,6 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - run: julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-docdeploy@latest
         env:

From b8520fc7b36be2ffcf75b67267e1c0265a167b6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Mon, 21 Apr 2025 14:29:37 -0400
Subject: [PATCH 11/16] Fix patch for Documenter on CI

---
 .github/workflows/Documenter.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/Documenter.yml b/.github/workflows/Documenter.yml
index 6b0146a..7d9be2a 100644
--- a/.github/workflows/Documenter.yml
+++ b/.github/workflows/Documenter.yml
@@ -12,6 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - run: julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
+      - run: cd docs && julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-docdeploy@latest
         env:

From 854867989b157f0813bc680b1dd50a3b339e3f6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Thu, 24 Apr 2025 12:23:17 -0400
Subject: [PATCH 12/16] Add missing handling for methods defined for external
 method tables

---
 src/codeedges.jl   | 24 +++++++++++-------------
 src/packagedef.jl  |  2 +-
 src/signatures.jl  |  8 +++++---
 test/signatures.jl | 16 ++++++++++++++--
 4 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/src/codeedges.jl b/src/codeedges.jl
index 647eae8..39c66c4 100644
--- a/src/codeedges.jl
+++ b/src/codeedges.jl
@@ -242,27 +242,25 @@ function direct_links!(cl::CodeLinks, src::CodeInfo)
             add_inner!(cl, icl, i)
             continue
         elseif isexpr(stmt, :method)
-            if length(stmt.args) === 3 && (arg3 = stmt.args[3]; arg3 isa CodeInfo)
-                icl = CodeLinks(cl.thismod, arg3)
-                add_inner!(cl, icl, i)
-            end
-            name = stmt.args[1]
-            if isa(name, GlobalRef) || isa(name, Symbol)
+            if length(stmt.args) === 1
+                # A function with no methods was defined. Associate its new binding to it.
+                name = stmt.args[1]
                 if isa(name, Symbol)
                     name = GlobalRef(cl.thismod, name)
                 end
-                assign = get(cl.nameassigns, name, nothing)
-                if assign === nothing
-                    cl.nameassigns[name] = assign = Int[]
+                if !isa(name, GlobalRef)
+                    @show stmt
+                    error("name ", typeof(name), " not recognized")
                 end
+                assign = get!(Vector{Int}, cl.nameassigns, name)
                 push!(assign, i)
                 targetstore = get!(Links, cl.namepreds, name)
                 target = P(name, targetstore)
                 add_links!(target, stmt, cl)
-            elseif name in (nothing, false)
-            else
-                @show stmt
-                error("name ", typeof(name), " not recognized")
+            elseif length(stmt.args) === 3 && (arg3 = stmt.args[3]; arg3 isa CodeInfo) # method definition
+                # A method was defined for an existing function.
+                icl = CodeLinks(cl.thismod, arg3)
+                add_inner!(cl, icl, i)
             end
             rhs = stmt
             target = P(SSAValue(i), cl.ssapreds[i])
diff --git a/src/packagedef.jl b/src/packagedef.jl
index c99cedd..b25c166 100644
--- a/src/packagedef.jl
+++ b/src/packagedef.jl
@@ -1,6 +1,6 @@
 Base.Experimental.@optlevel 1
 
-using Core: SimpleVector
+using Core: SimpleVector, MethodTable
 using Core.IR: CodeInfo, GotoIfNot, GotoNode, IR, MethodInstance, ReturnNode
 @static if isdefined(Core.IR, :EnterNode)
     using Core.IR: EnterNode
diff --git a/src/signatures.jl b/src/signatures.jl
index e533158..cf06690 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -53,7 +53,7 @@ function signature(@nospecialize(recurse), frame::Frame, @nospecialize(stmt), pc
         stmt = pc_expr(frame, pc)
     end
     isa(stmt, Expr) || return nothing, pc
-    mt = extract_method_table(frame, stmt; eval = false)
+    mt = extract_method_table(frame, stmt)
     sigsv = @lookup(frame, stmt.args[2])::SimpleVector
     sigt = signature(sigsv)
     return MethodInfoKey(mt, sigt), lastpc
@@ -189,7 +189,9 @@ function identify_framemethod_calls(frame)
             end
             msrc = stmt.args[3]
             if msrc isa CodeInfo
-                key = key::Union{GlobalRef,Bool,Nothing}
+                # XXX: Properly support interpolated `Core.MethodTable`. This will require using
+                # `stmt.args[2]` instead of `stmt.args[1]` to identify the parent function.
+                isa(key, Union{GlobalRef,Bool,Nothing}) || continue
                 for (j, mstmt) in enumerate(msrc.code)
                     isa(mstmt, Expr) || continue
                     jj = j
@@ -548,7 +550,7 @@ function methoddef!(@nospecialize(recurse), signatures::Vector{MethodInfoKey}, f
         if isa(meth, Method) && (meth.sig <: sigt && sigt <: meth.sig)
             push!(signatures, mt => meth.sig)
         else
-            if arg1 === false || arg1 === nothing
+            if arg1 === false || arg1 === nothing || isa(mt, MethodTable)
                 # If it's anonymous and not defined, define it
                 pc = step_expr!(recurse, frame, stmt, true)
                 meth = whichtt(sigt, mt)
diff --git a/test/signatures.jl b/test/signatures.jl
index dce60ce..ab281bc 100644
--- a/test/signatures.jl
+++ b/test/signatures.jl
@@ -505,9 +505,12 @@ end
 
 end
 
+module ExternalMT
+    Base.Experimental.@MethodTable method_table
+    macro overlay(ex) esc(:(Base.Experimental.@overlay $method_table $ex)) end
+end
+
 @testset "Support for external method tables" begin
-    ExternalMT = Module()
-    Core.eval(ExternalMT, :(Base.Experimental.@MethodTable method_table))
     signatures = MethodInfoKey[]
 
     ex = :(foo(x) = "foo")
@@ -525,6 +528,15 @@ end
     @test length(signatures) == 1
     (mt, sig) = pop!(signatures)
     @test (mt, sig) === (ExternalMT.method_table, Tuple{typeof(ExternalMT.foo), Any})
+
+    ex = :(@overlay foo(x::Int64) = "overlayed foo, second edition")
+    Core.eval(ExternalMT, ex)
+    frame = Frame(ExternalMT, ex)
+    pc = methoddefs!(signatures, frame; define = false)
+    @test length(signatures) == 1
+    (mt, sig) = pop!(signatures)
+    @test (mt, sig) === (ExternalMT.method_table, Tuple{typeof(ExternalMT.foo), Int64})
+    LoweredCodeUtils.identify_framemethod_calls(frame) # make sure this does not throw
 end
 
 end # module signatures

From 0b583871d02dd5b1b98d01c8af20fdfdd9607b9f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Belmant?= <cedric.belmant@juliahub.com>
Date: Fri, 25 Apr 2025 13:15:38 -0400
Subject: [PATCH 13/16] Adjust docs, add type annotations

---
 src/signatures.jl | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/signatures.jl b/src/signatures.jl
index 63114ad..3a3378c 100644
--- a/src/signatures.jl
+++ b/src/signatures.jl
@@ -24,9 +24,9 @@ function signature(sigsv::SimpleVector)
 end
 
 """
-    sigt, lastpc = signature([interp::Interpreter=RecursiveInterpreter()], frame::Frame, pc::Int)
+    (mt, sigt), lastpc = signature([interp::Interpreter=RecursiveInterpreter()], frame::Frame, pc::Int)
 
-Compute the signature-type `sigt` of a method whose definition in `frame` starts at `pc`.
+Compute the method table `mt` and signature-type `sigt` of a method whose definition in `frame` starts at `pc`.
 Generally, `pc` should point to the `Expr(:method, methname)` statement, in which case
 `lastpc` is the final statement number in `frame` that is part of the signature
 (i.e, the line above the 3-argument `:method` expression).
@@ -34,7 +34,7 @@ Alternatively, `pc` can point to the 3-argument `:method` expression,
 as long as all the relevant SSAValues have been assigned.
 In this case, `lastpc == pc`.
 
-If no 3-argument `:method` expression is found, `sigt` will be `nothing`.
+If no 3-argument `:method` expression is found, `nothing` will be returned in place of `(mt, sigt)`.
 """
 function signature(interp::Interpreter, frame::Frame, @nospecialize(stmt), pc::Int)
     mod = moduleof(frame)
@@ -620,9 +620,9 @@ function methoddef!(interp::Interpreter, signatures::Vector{MethodInfoKey}, fram
         stmt = pc_expr(frame, pc)  # there *should* be more statements in this frame
     end
 end
-methoddef!(interp::Interpreter, signatures, frame::Frame, pc::Int; define::Bool=true) =
+methoddef!(interp::Interpreter, signatures::Vector{MethodInfoKey}, frame::Frame, pc::Int; define::Bool=true) =
     methoddef!(interp, signatures, frame, pc_expr(frame, pc), pc; define)
-function methoddef!(interp::Interpreter, signatures, frame::Frame; define::Bool=true)
+function methoddef!(interp::Interpreter, signatures::Vector{MethodInfoKey}, frame::Frame; define::Bool=true)
     pc = frame.pc
     stmt = pc_expr(frame, pc)
     if !ismethod(stmt)
@@ -631,27 +631,27 @@ function methoddef!(interp::Interpreter, signatures, frame::Frame; define::Bool=
     pc === nothing && error("pc at end of frame without finding a method")
     methoddef!(interp, signatures, frame, pc; define)
 end
-methoddef!(signatures, frame::Frame, pc::Int; define::Bool=true) =
+methoddef!(signatures::Vector{MethodInfoKey}, frame::Frame, pc::Int; define::Bool=true) =
     methoddef!(RecursiveInterpreter(), signatures, frame, pc_expr(frame, pc), pc; define)
-methoddef!(signatures, frame::Frame; define::Bool=true) =
+methoddef!(signatures::Vector{MethodInfoKey}, frame::Frame; define::Bool=true) =
     methoddef!(RecursiveInterpreter(), signatures, frame; define)
 
-function methoddefs!(interp::Interpreter, signatures, frame::Frame, pc::Int; define::Bool=true)
+function methoddefs!(interp::Interpreter, signatures::Vector{MethodInfoKey}, frame::Frame, pc::Int; define::Bool=true)
     ret = methoddef!(interp, signatures, frame, pc; define)
     pc = ret === nothing ? ret : ret[1]
     return _methoddefs!(interp, signatures, frame, pc; define)
 end
-function methoddefs!(interp::Interpreter, signatures, frame::Frame; define::Bool=true)
+function methoddefs!(interp::Interpreter, signatures::Vector{MethodInfoKey}, frame::Frame; define::Bool=true)
     ret = methoddef!(interp, signatures, frame; define)
     pc = ret === nothing ? ret : ret[1]
     return _methoddefs!(interp, signatures, frame, pc; define)
 end
-methoddefs!(signatures, frame::Frame, pc::Int; define::Bool=true) =
+methoddefs!(signatures::Vector{MethodInfoKey}, frame::Frame, pc::Int; define::Bool=true) =
     methoddefs!(RecursiveInterpreter(), signatures, frame, pc; define)
-methoddefs!(signatures, frame::Frame; define::Bool=true) =
+methoddefs!(signatures::Vector{MethodInfoKey}, frame::Frame; define::Bool=true) =
     methoddefs!(RecursiveInterpreter(), signatures, frame; define)
 
-function _methoddefs!(interp::Interpreter, signatures, frame::Frame, pc::Int; define::Bool=define)
+function _methoddefs!(interp::Interpreter, signatures::Vector{MethodInfoKey}, frame::Frame, pc::Int; define::Bool=define)
     while pc !== nothing
         stmt = pc_expr(frame, pc)
         if !ismethod(stmt)

From b9853093f9e99fa6da0f658ee9426cb9ecbd7718 Mon Sep 17 00:00:00 2001
From: serenity4 <cedric.bel@hotmail.fr>
Date: Tue, 10 Jun 2025 15:28:26 +0200
Subject: [PATCH 14/16] Update CI dependency patch

---
 .github/workflows/CI.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index ed696af..cf14380 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -54,7 +54,7 @@ jobs:
             ${{ runner.os }}-test-${{ env.cache-name }}-
             ${{ runner.os }}-test-
             ${{ runner.os }}-
-      - run: julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
+      - run: julia --project -e 'using Pkg; Pkg.add([PackageSpec(; url="https://github.com/serenity4/JuliaInterpreter.jl", rev="codetracking-v2"), PackageSpec(; name = "CodeTracking", rev="master")])'
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
       - uses: julia-actions/julia-processcoverage@v1

From e624e99f1e16571752d40c10a2db1c7d4b16e81b Mon Sep 17 00:00:00 2001
From: serenity4 <cedric.bel@hotmail.fr>
Date: Tue, 10 Jun 2025 15:47:01 +0200
Subject: [PATCH 15/16] Test function definition, not method definition

---
 test/codeedges.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/codeedges.jl b/test/codeedges.jl
index 412620a..f1a9437 100644
--- a/test/codeedges.jl
+++ b/test/codeedges.jl
@@ -348,7 +348,7 @@ module ModSelective end
     edges = CodeEdges(ModEval, src)
     lr = lines_required(GlobalRef(ModEval, :revise538), src, edges)
     selective_eval_fromstart!(Frame(ModEval, src), lr, #=istoplevel=#true)
-    @test isdefined(ModEval, :revise538) && length(methods(ModEval.revise538, (Float32,))) == 1
+    @test isdefined(ModEval, :revise538) && isempty(methods(ModEval.revise538)) # function is defined, method is not
 
     # https://github.com/timholy/Revise.jl/issues/599
     thk = Meta.lower(Main, quote

From 8d8784f88f16d950f2e5671c6015fbbb2805f924 Mon Sep 17 00:00:00 2001
From: serenity4 <cedric.bel@hotmail.fr>
Date: Tue, 10 Jun 2025 15:49:39 +0200
Subject: [PATCH 16/16] Update CI docs dependency patch

---
 .github/workflows/Documenter.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/Documenter.yml b/.github/workflows/Documenter.yml
index 7d9be2a..3397e84 100644
--- a/.github/workflows/Documenter.yml
+++ b/.github/workflows/Documenter.yml
@@ -11,8 +11,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - run: julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
-      - run: cd docs && julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 https://github.com/serenity4/CodeTracking.jl#parametrize-by-mt"'
+      - run: julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 CodeTracking#master"'
+      - run: cd docs && julia --project -e 'using Pkg; pkg"add https://github.com/serenity4/JuliaInterpreter.jl#codetracking-v2 CodeTracking#master"'
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-docdeploy@latest
         env: