Prevent excessive specialization for the flamegraphitem function

Before this change, this would specialize in two undesireable
ways (at least on Julia v1.7): almost every tree node has a different
type (depending on its depth) and for the output function,
closures wrap closures in a long tower, which also gives different
types for each.

Author: tkluck

haml/flamegraph.hamljl

@@ -14,6 +14,6 @@
   %rect(x=0.0, y=0, width=1200.0, height=height, fill="url(#background)")/
   %text(text_anchor="", x=10.0, y=height, font_size=12, font_family="Verdana",
         fill="rgb(0,0,0)", dominant_baseline="ideographic", id="details")= " "
-  - @include("flamegraphitem.hamljl", report=$report, node=$report.flamegraph,
+  - @include("flamegraphitem.hamljl", report=$report, node=Ref{Any}($report.flamegraph),
         x=Ref(0.0), y=height-20-16, scale = 1200.0 / $report.tracecount)
 -# vim: set filetype=haml:

haml/flamegraphitem.hamljl

@@ -1,5 +1,5 @@
-- pt = TracePoint($node.data.sf)
-- span = $node.data.span
+- pt = TracePoint($node[].data.sf)
+- span = $node[].data.span
 - cnt = length(span)
 - width = $scale * cnt
 - label = pt.containing_function.name
@@ -17,8 +17,8 @@
     %rect(x=$x[], y=$y, width=width, height=15.0, fill=fillcolor, rx=2, ry=2)/
     %text(text_anchor="", x=$x[] + 3, y=$y + 10.5, font_size=12, font_family="Verdana", fill="rgb(0,0,0)")= show_label ? label : " "
 - curx = Ref($x[])
-- for child in $node
-  - @include("flamegraphitem.hamljl", report=$report, node=child,
+- for child in $node[]
+  - @output render_flamegraphitem(report=$report, node=Ref{Any}(child),
         x=curx, y=$y - 16, scale=$scale)
 - $x[] += width
 -# vim: set filetype=haml:

src/HTML.jl

@@ -3,7 +3,7 @@ module HTML
 import Base64: base64encode
 
 import Dates: format, RFC1123Format
-import HAML: includehaml, @include, @surround, @cdatafile
+import HAML: includehaml, @include, @surround, @cdatafile, @output
 
 import ..Reports: Report, FunctionPoint, TracePoint
 
@@ -15,6 +15,7 @@ includehaml(@__MODULE__,
     :render_files      => templatefile("files.hamljl"),
     :render_methods    => templatefile("methods.hamljl"),
     :render_flamegraph => templatefile("flamegraph.hamljl"),
+    :render_flamegraphitem => templatefile("flamegraphitem.hamljl"),
 )
 
 outputfilename(::Nothing) = ""