inference: fix the correctness of inference bail out interface (#48826)

Since we allow overloading of the `bail_out_xxx` hooks, we need to make
sure that we widen both type and effects to the top when bailing on
inference regardless of the condition presumed by a hook.

This commit particularly fixes the correctness of `bail_out_apply`
(fixes #48807). I wanted to make a simplified test case for this, but
it turns out to be a bit tricky since it relies on the details of
multiple match analysis and the bail out logic.

base/compiler/abstractinterpretation.jl

@@ -111,10 +111,9 @@ function abstract_call_gf_by_type(interp::AbstractInterpreter, @nospecialize(f),
         match = applicable[i]::MethodMatch
         method = match.method
         sig = match.spec_types
-        if bail_out_toplevel_call(interp, sig, sv)
+        if bail_out_toplevel_call(interp, InferenceLoopState(sig, rettype, all_effects), sv)
             # only infer concrete call sites in top-level expressions
             add_remark!(interp, sv, "Refusing to infer non-concrete call site in top-level expression")
-            rettype = Any
             break
         end
         this_rt = Bottom
@@ -191,7 +190,8 @@ function abstract_call_gf_by_type(interp::AbstractInterpreter, @nospecialize(f),
                 conditionals[2][i] = tmerge(conditionals[2][i], cnd.elsetype)
             end
         end
-        if bail_out_call(interp, rettype, sv)
+        if bail_out_call(interp, InferenceLoopState(sig, rettype, all_effects), sv)
+            add_remark!(interp, sv, "Call inference reached maximally imprecise information. Bailing on.")
             break
         end
     end
@@ -201,7 +201,9 @@ function abstract_call_gf_by_type(interp::AbstractInterpreter, @nospecialize(f),
         info = ConstCallInfo(info, const_results)
     end
 
-    if seen != napplicable
+    if seen ≠ napplicable
+        # there is unanalyzed candidate, widen type and effects to the top
+        rettype = Any
         # there may be unanalyzed effects within unseen dispatch candidate,
         # but we can still ignore nonoverlayed effect here since we already accounted for it
         all_effects = merge_effects(all_effects, EFFECTS_UNKNOWN)
@@ -1529,7 +1531,9 @@ function abstract_apply(interp::AbstractInterpreter, argtypes::Vector{Any}, si::
     end
     retinfos = ApplyCallInfo[]
     retinfo = UnionSplitApplyCallInfo(retinfos)
-    for i = 1:length(ctypes)
+    napplicable = length(ctypes)
+    seen = 0
+    for i = 1:napplicable
         ct = ctypes[i]
         arginfo = infos[i]
         lct = length(ct)
@@ -1543,17 +1547,21 @@ function abstract_apply(interp::AbstractInterpreter, argtypes::Vector{Any}, si::
             end
         end
         call = abstract_call(interp, ArgInfo(nothing, ct), si, sv, max_methods)
+        seen += 1
         push!(retinfos, ApplyCallInfo(call.info, arginfo))
         res = tmerge(res, call.rt)
         effects = merge_effects(effects, call.effects)
-        if bail_out_apply(interp, res, sv)
-            if i != length(ctypes)
-                # No point carrying forward the info, we're not gonna inline it anyway
-                retinfo = NoCallInfo()
-            end
+        if bail_out_apply(interp, InferenceLoopState(ct, res, effects), sv)
+            add_remark!(interp, sv, "_apply_iterate inference reached maximally imprecise information. Bailing on.")
             break
         end
     end
+    if seen ≠ napplicable
+        # there is unanalyzed candidate, widen type and effects to the top
+        res = Any
+        effects = Effects()
+        retinfo = NoCallInfo() # NOTE this is necessary to prevent the inlining processing
+    end
     # TODO: Add a special info type to capture all the iteration info.
     # For now, only propagate info if we don't also union-split the iteration
     return CallMeta(res, effects, retinfo)

base/compiler/inferencestate.jl

@@ -221,14 +221,23 @@ is_effect_overridden(override::EffectsOverride, effect::Symbol) = getfield(overr
 
 add_remark!(::AbstractInterpreter, sv::Union{InferenceState, IRCode}, remark) = return
 
-function bail_out_toplevel_call(::AbstractInterpreter, @nospecialize(callsig), sv::Union{InferenceState, IRCode})
-    return isa(sv, InferenceState) && sv.restrict_abstract_call_sites && !isdispatchtuple(callsig)
+struct InferenceLoopState
+    sig
+    rt
+    effects::Effects
+    function InferenceLoopState(@nospecialize(sig), @nospecialize(rt), effects::Effects)
+        new(sig, rt, effects)
+    end
+end
+
+function bail_out_toplevel_call(::AbstractInterpreter, state::InferenceLoopState, sv::Union{InferenceState, IRCode})
+    return isa(sv, InferenceState) && sv.restrict_abstract_call_sites && !isdispatchtuple(state.sig)
 end
-function bail_out_call(::AbstractInterpreter, @nospecialize(rt), sv::Union{InferenceState, IRCode})
-    return rt === Any
+function bail_out_call(::AbstractInterpreter, state::InferenceLoopState, sv::Union{InferenceState, IRCode})
+    return state.rt === Any
 end
-function bail_out_apply(::AbstractInterpreter, @nospecialize(rt), sv::Union{InferenceState, IRCode})
-    return rt === Any
+function bail_out_apply(::AbstractInterpreter, state::InferenceLoopState, sv::Union{InferenceState, IRCode})
+    return state.rt === Any
 end
 
 was_reached(sv::InferenceState, pc::Int) = sv.ssavaluetypes[pc] !== NOT_FOUND