single scan for slot ids [ci skip]

base/interactiveutil.jl

@@ -346,31 +346,28 @@ This serves as a warning of potential type instability. Not all non-leaf types a
 problematic for performance, so the results need to be used judiciously.
 See [`@code_warntype`](@ref man-code-warntype) for more information.
 """
-function code_warntype(io::IO, f, @nospecialize(t))
-    function is_variable_used(bodies::Vector, slotnames, v)
-        for body in bodies
-            is_variable_used(body, slotnames, v) && return true
+function code_warntype(io::IO, f, t::ANY) #@nospecialize(t))
+    function find_used_slotids(cinfo::CodeInfo)
+        used_slotids = Set{Int}()
+        for node in cinfo.code
+            populate_slotids!(used_slotids, node)
         end
-        return false
+        return used_slotids
     end
 
-    function is_variable_used(expr::Expr, slotnames, v)
-        for arg in expr.args
-            is_variable_used(arg, slotnames, v) && return true
-        end
-        return false
-    end
-
-    is_variable_used(arg::SlotNumber, slotnames, v) = slotnames[arg.id] == v
-    is_variable_used(arg, slotnames, v) = false
+    populate_slotids!(used_slotids, arg::Vector) = foreach(x -> populate_slotids!(used_slotids, x), arg)
+    populate_slotids!(used_slotids, arg::Expr) = foreach(x -> populate_slotids!(used_slotids, x), arg.args)
+    populate_slotids!(used_slotids, arg::Slot) = push!(used_slotids, arg.id)
+    populate_slotids!(used_slotids, arg) = used_slotids
 
     emph_io = IOContext(io, :TYPEEMPHASIZE => true)
     for (src, rettype) in code_typed(f, t)
+        used_slotids = find_used_slotids(src)
         println(emph_io, "Variables:")
         slotnames = sourceinfo_slotnames(src)
         for i = 1:length(slotnames)
             print(emph_io, "  ", slotnames[i])
-            isused = is_variable_used(src.code, slotnames, slotnames[i])
+            isused = i in used_slotids
             if isa(src.slottypes, Array)
                 show_expr_type(emph_io, src.slottypes[i], isused)
             end