From ee623e44b974e9d7a1e6ba89dc092b97c131f9fd Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Tue, 30 Aug 2016 19:29:52 -0400
Subject: [PATCH] remove pessimistic "UNION_SPLIT_MISMATCH_ERROR" from
 inference

---
 base/inference.jl | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/base/inference.jl b/base/inference.jl
index 9444ad0a049d3..0d91d4127ee28 100644
--- a/base/inference.jl
+++ b/base/inference.jl
@@ -10,7 +10,6 @@ const MAX_TUPLE_DEPTH = 4
 
 const MAX_TUPLE_SPLAT = 16
 const MAX_UNION_SPLITTING = 4
-const UNION_SPLIT_MISMATCH_ERROR = false
 
 # alloc_elim_pass! relies on `Slot_AssignedOnce | Slot_UsedUndef` being
 # SSA. This should be true now but can break if we start to track conditional
@@ -834,13 +833,6 @@ function abstract_call_gf_by_type(f::ANY, atype::ANY, sv::InferenceState)
         return Any
     end
     x::Array{Any,1} = applicable
-    if isempty(x)
-        # no methods match
-        # TODO: it would be nice to return Bottom here, but during bootstrap we
-        # often compile code that calls methods not defined yet, so it is much
-        # safer just to fall back on dynamic dispatch.
-        return Any
-    end
     fullmatch = false
     for (m::SimpleVector) in x
         sig = m[1]::DataType
@@ -965,7 +957,10 @@ function abstract_call_gf_by_type(f::ANY, atype::ANY, sv::InferenceState)
         # added that did not intersect with any existing method
         add_mt_backedge(ft.name.mt, argtype, sv)
     end
-    # if rettype is Bottom we've found a method not found error
+    if isempty(x)
+        # TODO: this is needed because type intersection is wrong in some cases
+        return Any
+    end
     #print("=> ", rettype, "\n")
     return rettype
 end
@@ -2627,7 +2622,7 @@ function inlineable(f::ANY, ft::ANY, e::Expr, atypes::Vector{Any}, sv::Inference
                                 all = false
                             end
                         end
-                        if UNION_SPLIT_MISMATCH_ERROR && all
+                        if all
                             error_label === nothing && (error_label = genlabel(sv))
                             push!(stmts, GotoNode(error_label.label))
                         else
@@ -2646,7 +2641,7 @@ function inlineable(f::ANY, ft::ANY, e::Expr, atypes::Vector{Any}, sv::Inference
                 append!(stmts, match)
                 if error_label !== nothing
                     push!(stmts, error_label)
-                    push!(stmts, Expr(:call, GlobalRef(_topmod(sv.mod), :error), "error in type inference due to #265"))
+                    push!(stmts, Expr(:call, GlobalRef(_topmod(sv.mod), :error), "fatal error in type inference (type bound)"))
                 end
                 local ret_var, merge
                 if spec_miss !== nothing
@@ -2910,7 +2905,7 @@ function inlineable(f::ANY, ft::ANY, e::Expr, atypes::Vector{Any}, sv::Inference
     lastexpr = pop!(body.args)
     if isa(lastexpr,LabelNode)
         push!(body.args, lastexpr)
-        push!(body.args, Expr(:call, GlobalRef(_topmod(sv.mod),:error), "fatal error in type inference"))
+        push!(body.args, Expr(:call, GlobalRef(_topmod(sv.mod), :error), "fatal error in type inference (lowering)"))
         lastexpr = nothing
     elseif !(isa(lastexpr,Expr) && lastexpr.head === :return)
         # code sometimes ends with a meta node, e.g. inbounds pop