bpart: Give a warning when accessing a backdated const binding (JuliaLang#57133)

This implements the strategy proposed in
JuliaLang#57102 (comment).
Example:
```
julia> function foo(i)
           eval(:(const x = $i))
           x
       end
foo (generic function with 1 method)

julia> foo(1)
WARNING: Detected access to binding Main.x in a world prior to its definition world.
  Julia 1.12 has introduced more strict world age semantics for global bindings.
  !!! This code may malfunction under Revise.
  !!! This code will error in future versions of Julia.
Hint: Add an appropriate `invokelatest` around the access to this binding.
1
```

The warning is triggered once per binding to avoid spamming for repeated
access.

Author: Keno

src/Compiler.jl

@@ -49,7 +49,8 @@ using Core: ABIOverride, Builtin, CodeInstance, IntrinsicFunction, MethodInstanc
 
 using Base
 using Base: @_foldable_meta, @_gc_preserve_begin, @_gc_preserve_end, @nospecializeinfer,
-    BINDING_KIND_GLOBAL, BINDING_KIND_UNDEF_CONST, Base, BitVector, Bottom, Callable, DataTypeFieldDesc,
+    BINDING_KIND_GLOBAL, BINDING_KIND_UNDEF_CONST, BINDING_KIND_BACKDATED_CONST,
+    Base, BitVector, Bottom, Callable, DataTypeFieldDesc,
     EffectsOverride, Filter, Generator, IteratorSize, JLOptions, NUM_EFFECTS_OVERRIDES,
     OneTo, Ordering, RefValue, SizeUnknown, _NAMEDTUPLE_NAME,
     _array_for, _bits_findnext, _methods_by_ftype, _uniontypes, all, allocatedinline, any,

src/abstractinterpretation.jl

@@ -3524,6 +3524,11 @@ function abstract_eval_partition_load(interp::AbstractInterpreter, partition::Co
     end
 
     if is_defined_const_binding(kind)
+        if kind == BINDING_KIND_BACKDATED_CONST
+            # Infer this as guard. We do not want a later const definition to retroactively improve
+            # inference results in an earlier world.
+            return RTEffects(Any, UndefVarError, generic_getglobal_effects)
+        end
         rt = Const(partition_restriction(partition))
         return RTEffects(rt, Union{}, Effects(EFFECTS_TOTAL, inaccessiblememonly=is_mutation_free_argtype(rt) ? ALWAYS_TRUE : ALWAYS_FALSE))
     end

src/ssair/slot2ssa.jl

@@ -137,10 +137,6 @@ function fixemup!(@specialize(slot_filter), @specialize(rename_slot), ir::IRCode
                 return nothing
             end
             op[] = x
-        elseif isa(val, GlobalRef) && !(isdefined(val.mod, val.name) && isconst(val.mod, val.name))
-            typ = typ_for_val(val, ci, ir, idx, Any[])
-            new_inst = NewInstruction(val, typ)
-            op[] = NewSSAValue(insert_node!(ir, idx, new_inst).id - length(ir.stmts))
         elseif isexpr(val, :static_parameter)
             ty = typ_for_val(val, ci, ir, idx, Any[])
             if isa(ty, Const)

src/ssair/verify.jl

@@ -121,7 +121,7 @@ function verify_ir(ir::IRCode, print::Bool=true,
         if mi !== nothing
             push!(error_args, "\n", "  Method instance: ", mi)
         end
-        error(error_args...)
+        invokelatest(error, error_args...)
     end
     # Verify CFG graph. Must be well formed to construct domtree
     if !(length(ir.cfg.blocks) - 1 <= length(ir.cfg.index) <= length(ir.cfg.blocks))
@@ -380,6 +380,15 @@ function verify_ir(ir::IRCode, print::Bool=true,
                         # undefined GlobalRef is OK in isdefined
                         continue
                     end
+                elseif stmt.head === :throw_undef_if_not
+                    if length(stmt.args) > 3
+                        @verify_error "malformed throw_undef_if_not"
+                        raise_error()
+                    end
+                    if stmt.args[1] isa GlobalRef
+                        # undefined GlobalRef is OK in throw_undef_if_not
+                        continue
+                    end
                 elseif stmt.head === :gc_preserve_end
                     # We allow gc_preserve_end tokens to span across try/catch
                     # blocks, which isn't allowed for regular SSA values, so

test/invalidation.jl

@@ -55,7 +55,7 @@ let mi = Base.method_instance(basic_caller, (Float64,))
 end
 
 # this redefinition below should invalidate the cache
-const BASIC_CALLER_WORLD = Base.get_world_counter()
+const BASIC_CALLER_WORLD = Base.get_world_counter()+1
 basic_callee(x) = x, x
 @test !isdefined(Base.method_instance(basic_callee, (Float64,)), :cache)
 let mi = Base.method_instance(basic_caller, (Float64,))