inference: simplify error-case handling within `abstract_eval_stateme…

…nt` (JuliaLang#46119)

base/compiler/abstractinterpretation.jl

@@ -1968,7 +1968,7 @@ function abstract_eval_statement(interp::AbstractInterpreter, @nospecialize(e),
  ismutable = ismutabletype(t)
  fcount = fieldcount(t)
  nargs = length(e.args) - 1
- is_nothrow && (is_nothrow = fcount ≥ nargs)
+ @assert fcount ≥ nargs "malformed :new expression" # syntactically enforced by the front-end
  ats = Vector{Any}(undef, nargs)
  local anyrefine = false
  local allconst = true
@@ -1977,11 +1977,7 @@ function abstract_eval_statement(interp::AbstractInterpreter, @nospecialize(e),
  ft = fieldtype(t, i)
  is_nothrow && (is_nothrow = at ⊑ ft)
  at = tmeet(at, ft)
- if at === Bottom
- t = Bottom
- tristate_merge!(sv, EFFECTS_THROWS)
- @goto t_computed
- end
+ at === Bottom && @goto always_throw
  if ismutable && !isconst(t, i)
  ats[i] = ft # can't constrain this field (as it may be modified later)
  continue
@@ -2060,9 +2056,7 @@ function abstract_eval_statement(interp::AbstractInterpreter, @nospecialize(e),
  t = sp_type_rewrap(e.args[2], sv.linfo, true)
  for i = 3:length(e.args)
  if abstract_eval_value(interp, e.args[i], vtypes, sv) === Bottom
- t = Bottom
- tristate_merge!(sv, EFFECTS_THROWS)
- @goto t_computed
+ @goto always_throw
  end
  end
  effects = EFFECTS_UNKNOWN
@@ -2122,10 +2116,13 @@ function abstract_eval_statement(interp::AbstractInterpreter, @nospecialize(e),
  end
  end
  end
+ elseif false
+ @label always_throw
+ t = Bottom
+ tristate_merge!(sv, EFFECTS_THROWS)
  else
  t = abstract_eval_value_expr(interp, e, vtypes, sv)
  end
- @label t_computed
  @assert !isa(t, TypeVar) "unhandled TypeVar"
  if isa(t, DataType) && isdefined(t, :instance)
  # replace singleton types with their equivalent Const object