From 43235e9cc3fe4e790e4ad04f39b7d00b22fa71d9 Mon Sep 17 00:00:00 2001
From: Elliot Saba <staticfloat@gmail.com>
Date: Tue, 7 Feb 2023 20:57:00 +0000
Subject: [PATCH] [compiler] Teach type inference that `GotoIfNot` can throw

Previously, the effects system would ignore certain cases where
`GotoIfNot` nodes would be capable of throwing; this resulted in simple
examples such as the following being marked as `nothrow`:

```
julia> foo(x) = x > 0 ? x : 0
       Base.infer_effects(foo, (Missing,))
(+c,+e,+n,+t,+s,+m,+i)
```

With this change, we correctly notice when a `GotoIfNot` node is given a
non-`Bool` condition, annotate the basic block as possibly throwing, and
further end type inference if the condition is provably non-`Bool`.
---
 base/compiler/abstractinterpretation.jl | 9 +++++++++
 test/compiler/effects.jl                | 8 ++++++++
 2 files changed, 17 insertions(+)

diff --git a/base/compiler/abstractinterpretation.jl b/base/compiler/abstractinterpretation.jl
index 58d4cbf10a82c..ef49d56895890 100644
--- a/base/compiler/abstractinterpretation.jl
+++ b/base/compiler/abstractinterpretation.jl
@@ -2893,6 +2893,7 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                         empty!(frame.pclimitations)
                         @goto find_next_bb
                     end
+                    orig_condt = condt
                     if !(isa(condt, Const) || isa(condt, Conditional)) && isa(condx, SlotNumber)
                         # if this non-`Conditional` object is a slot, we form and propagate
                         # the conditional constraint on it
@@ -2924,6 +2925,14 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                             handle_control_backedge!(interp, frame, currpc, stmt.dest)
                             @goto branch
                         else
+                            if !⊑(𝕃ᵢ, orig_condt, Bool)
+                                merge_effects!(interp, frame, EFFECTS_THROWS)
+                                if !hasintersect(widenconst(orig_condt), Bool)
+                                    ssavaluetypes[currpc] = Bottom
+                                    @goto find_next_bb
+                                end
+                            end
+
                             # We continue with the true branch, but process the false
                             # branch here.
                             if isa(condt, Conditional)
diff --git a/test/compiler/effects.jl b/test/compiler/effects.jl
index 656ac9268dcb4..048e5146e2dcb 100644
--- a/test/compiler/effects.jl
+++ b/test/compiler/effects.jl
@@ -743,3 +743,11 @@ end
 
 @test Base.ismutationfree(Type{Union{}})
 @test Core.Compiler.is_total(Base.infer_effects(typejoin, ()))
+
+
+# GotoIfNot should properly mark itself as throwing when given a non-Bool
+# https://github.com/JuliaLang/julia/pull/48583
+gotoifnot_throw_check_48583(x) = x ? x : 0
+@test !Core.Compiler.is_nothrow(Base.infer_effects(gotoifnot_throw_check_48583, (Missing,)))
+@test !Core.Compiler.is_nothrow(Base.infer_effects(gotoifnot_throw_check_48583, (Any,)))
+@test Core.Compiler.is_nothrow(Base.infer_effects(gotoifnot_throw_check_48583, (Bool,)))