fix _builtin_nothrow for arrayset (#46105)

Author: aviatesk

base/compiler/tfuncs.jl

@@ -1697,7 +1697,7 @@ end
 # Query whether the given builtin is guaranteed not to throw given the argtypes
 function _builtin_nothrow(@nospecialize(f), argtypes::Array{Any,1}, @nospecialize(rt))
     if f === arrayset
-        array_builtin_common_nothrow(argtypes, 4) || return true
+        array_builtin_common_nothrow(argtypes, 4) || return false
         # Additionally check element type compatibility
         return arrayset_typecheck(argtypes[2], argtypes[3])
     elseif f === arrayref || f === const_arrayref

test/compiler/effects.jl

@@ -171,3 +171,8 @@ let effects = Base.infer_effects(f_setfield_nothrow, ())
     #@test Core.Compiler.is_effect_free(effects)
     @test Core.Compiler.is_nothrow(effects)
 end
+
+# nothrow for arrayset
+@test Base.infer_effects((Vector{Int},Int)) do a, i
+    a[i] = 0 # may throw
+end |> !Core.Compiler.is_nothrow