eval() without jl_begin_new_module for julia 1.11

It turns out it's possible to implement eval against an iterative
lowering API even without the ability to begin and end a module - we
just need to generate the right call expression within the module to
recursively call the eval implementation.

Author: c42f

src/eval.jl

@@ -439,8 +439,14 @@ end
 @fzone "JL: eval" function eval(mod::Module, ex::SyntaxTree;
                                 macro_world::UInt=Base.get_world_counter(),
                                 opts...)
-    modules = Module[]
     iter = lower_init(ex, mod, macro_world; opts...)
+    _eval(mod, iter)
+end
+
+if VERSION >= v"1.13.0-DEV.1199" # https://github.com/JuliaLang/julia/pull/59604
+
+function _eval(mod, iter)
+    modules = Module[]
     new_mod = nothing
     result = nothing
     while true
@@ -467,6 +473,37 @@ end
     return result
 end
 
+else
+
+function _eval(mod, iter, new_mod=nothing)
+    in_new_mod = !isnothing(new_mod)
+    result = nothing
+    while true
+        thunk = lower_step(iter, new_mod)::Core.SimpleVector
+        new_mod = nothing
+        type = thunk[1]::Symbol
+        if type == :done
+            @assert !in_new_mod
+            break
+        elseif type == :begin_module
+            name = thunk[2]::Symbol
+            std_defs = thunk[3]
+            result = Core.eval(mod,
+                Expr(:module, std_defs, name,
+                     Expr(:block, thunk[4], Expr(:call, m->_eval(m, iter, m), name)))
+            )
+        elseif type == :end_module
+            @assert in_new_mod
+            return mod
+        else
+            @assert type == :thunk
+            result = Core.eval(mod, thunk[2])
+        end
+    end
+    return result
+end
+
+end
 
 """
     include(mod::Module, path::AbstractString)