inference: handle cases where :the_exception is used independently (JuliaLang#56836)

`Expr(:the_exception)` is handled by the interpreter in all cases,
however, inference assumes it is only used within frames containing
`try/catch`. This commit corrects that assumption.

Author: aviatesk

Compiler/src/abstractinterpretation.jl

@@ -3240,8 +3240,16 @@ function abstract_eval_throw_undef_if_not(interp::AbstractInterpreter, e::Expr,
 end
 
 function abstract_eval_the_exception(::AbstractInterpreter, sv::InferenceState)
-    (;handlers, handler_at) = sv.handler_info::HandlerInfo
-    return the_exception_info(handlers[handler_at[sv.currpc][2]].exct)
+    (;handler_info) = sv
+    if handler_info === nothing
+        return the_exception_info(Any)
+    end
+    (;handlers, handler_at) = handler_info
+    handler_id = handler_at[sv.currpc][2]
+    if handler_id === 0
+        return the_exception_info(Any)
+    end
+    return the_exception_info(handlers[handler_id].exct)
 end
 abstract_eval_the_exception(::AbstractInterpreter, ::IRInterpretationState) = the_exception_info(Any)
 the_exception_info(@nospecialize t) = RTEffects(t, Union{}, Effects(EFFECTS_TOTAL; consistent=ALWAYS_FALSE))

Compiler/test/inference.jl

@@ -6125,3 +6125,17 @@ function func_swapglobal!_must_throw(x)
 end
 @test Base.infer_return_type(func_swapglobal!_must_throw, (Int,); interp=SwapGlobalInterp()) === Union{}
 @test !Compiler.is_effect_free(Base.infer_effects(func_swapglobal!_must_throw, (Int,); interp=SwapGlobalInterp()) )
+
+@eval get_exception() = $(Expr(:the_exception))
+@test Base.infer_return_type() do
+    get_exception()
+end <: Any
+@test @eval Base.infer_return_type((Float64,)) do x
+    out = $(Expr(:the_exception))
+    try
+        out = sin(x)
+    catch
+        out = $(Expr(:the_exception))
+    end
+    return out
+end == Union{Float64,DomainError}