WIP: Make hasmethod able to be used for static dispatch

base/compiler/typeinfer.jl

@@ -176,29 +176,26 @@ function store_backedges(frame::InferenceState)
     if !toplevel && (frame.cached || frame.parent !== nothing)
         caller = frame.result.linfo
         for edges in frame.stmt_edges
-            edges === nothing && continue
-            i = 1
-            while i <= length(edges)
-                to = edges[i]
-                if isa(to, MethodInstance)
-                    ccall(:jl_method_instance_add_backedge, Cvoid, (Any, Any), to, caller)
-                    i += 1
-                else
-                    typeassert(to, Core.MethodTable)
-                    typ = edges[i + 1]
-                    ccall(:jl_method_table_add_backedge, Cvoid, (Any, Any, Any), to, typ, caller)
-                    i += 2
-                end
-            end
+            store_backedges(caller, edges)
         end
-        edges = frame.src.edges
-        if edges !== nothing
-            edges = edges::Vector{MethodInstance}
-            for edge in edges
-                @assert isa(edge, MethodInstance)
-                ccall(:jl_method_instance_add_backedge, Cvoid, (Any, Any), edge, caller)
-            end
-            frame.src.edges = nothing
+        store_backedges(caller, frame.src.edges)
+        frame.src.edges = nothing
+    end
+end
+
+store_backedges(caller, edges::Nothing) = nothing
+function store_backedges(caller, edges::Vector)
+    i = 1
+    while i <= length(edges)
+        to = edges[i]
+        if isa(to, MethodInstance)
+            ccall(:jl_method_instance_add_backedge, Cvoid, (Any, Any), to, caller)
+            i += 1
+        else
+            typeassert(to, Core.MethodTable)
+            typ = edges[i + 1]
+            ccall(:jl_method_table_add_backedge, Cvoid, (Any, Any, Any), to, typ, caller)
+            i += 2
         end
     end
 end

base/essentials.jl

@@ -234,10 +234,11 @@ function unwrap_unionall(@nospecialize(a))
 end
 
 function rewrap_unionall(@nospecialize(t), @nospecialize(u))
-    if !isa(u, UnionAll)
+    if isa(u, UnionAll)
+        return UnionAll(u.var, rewrap_unionall(t, u.body))
+    else
         return t
     end
-    return UnionAll(u.var, rewrap_unionall(t, u.body))
 end
 
 # replace TypeVars in all enclosing UnionAlls with fresh TypeVars

base/reflection.jl

@@ -1238,12 +1238,65 @@ julia> hasmethod(g, Tuple{}, (:a, :b, :c, :d))  # g accepts arbitrary kwargs
 true
 ```
 """
-function hasmethod(@nospecialize(f), @nospecialize(t); world=typemax(UInt))
+function hasmethod end
+
+# This is just declaring a simplified version of `@generated` earlier in bootstrappping
+# to be used by hasmethod. TODO: Replace this with just using @eval ?
+macro _early_generated(headsig, body)
+    return Expr(:escape,
+                Expr(:function, headsig,
+                     Expr(:block,
+                          Expr(:if, Expr(:generated),
+                               body,
+                               Expr(:block,
+                                    Expr(:meta, :generated_only),
+                                    Expr(:return, nothing))))))
+end
+
+# This is used to create the CodeInfo returned by hasmethod in the case of false.
+_hasmethod_false(@nospecialize(f), @nospecialize(t), @nospecialize(w)) = false
+
+@_early_generated(
+    static_hasmethod(
+        @nospecialize(f),
+        @nospecialize(t::Type{T}),
+        @nospecialize(world::Val{W})
+    ) where {T<:Tuple, W},
+    begin
+        # The signature type:
+        typ = rewrap_unionall(Tuple{f, unwrap_unionall(T).parameters...}, T)
+
+        method_doesnot_exist = ccall(:jl_gf_invoke_lookup, Any, (Any, UInt), typ, W) === nothing
+        if method_doesnot_exist
+            ci_orig = uncompressed_ast(typeof(_hasmethod_false).name.mt.defs.func)
+            ci = ccall(:jl_copy_code_info, Ref{CodeInfo}, (Any,), ci_orig)
+
+            # Now we add the edges so if a method is defined this recompiles
+            mt = f.name.mt
+            ci.edges = Core.Compiler.vect(mt, typ)
+            return ci
+        else
+            return true  # We are done, it exists, no need to recompile ever
+            # except if it is deleted. TODO: deal with Base.delete_method
+        end
+    end
+)
+
+function static_hasmethod(@nospecialize(f), @nospecialize(t); world=typemax(UInt))
+    return static_hasmethod(f, t, Val{world}())
+end
+
+
+function dynamic_hasmethod(@nospecialize(f), @nospecialize(t); world=typemax(UInt))
     t = to_tuple_type(t)
     t = signature_type(f, t)
     return ccall(:jl_gf_invoke_lookup, Any, (Any, UInt), t, world) !== nothing
 end
 
+function hasmethod(@nospecialize(f), @nospecialize(t); world=typemax(UInt))
+    return static_hasmethod(f, t; world=world)
+end
+
 function hasmethod(@nospecialize(f), @nospecialize(t), kwnames::Tuple{Vararg{Symbol}}; world=typemax(UInt))
     # TODO: this appears to be doing the wrong queries
     hasmethod(f, t, world=world) || return false