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Fix @nospecialize with zero args #112

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2c8a478
`expr_to_syntaxtree`: don't fail when incoming expr is invalid
mlechu Oct 16, 2025
7bb1747
Fix `@nospecialize` with zero args
mlechu Oct 29, 2025
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173 changes: 84 additions & 89 deletions src/compat.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -11,13 +11,15 @@ end

"""
An Expr -> SyntaxTree transformation that should preserve semantics, but will
have low-quality provenance info (namely, each tree node will be associated with
the last seen LineNumberNode in the pre-order expr traversal).
produce low-quality provenance info (namely, each tree node will be associated
with the last seen LineNumberNode in the pre-order expr traversal).

Last-resort option so that, for example, we can lower the output of old
Expr-producing macros. Always prefer re-parsing source text over using this.

Supports parsed and/or macro-expanded exprs, but not lowered exprs
Supports parsed and/or macro-expanded exprs, but not lowered exprs. Since
macrocall and quote may occur in this tree, we can't throw errors for malformed
syntax; we can only convert known-good exprs that have a SyntaxTree equivalent.
"""
function expr_to_syntaxtree(@nospecialize(e), lnn::Union{LineNumberNode, Nothing}=nothing)
graph = ensure_attributes!(
Expand Down Expand Up @@ -46,22 +48,22 @@ end
return out
end

function _expr_replace!(@nospecialize(e), replace_pred::Function, replacer!::Function,
function _expr_replace(@nospecialize(e), replace_pred::Function, replacer::Function,
recurse_pred=(@nospecialize e)->true)
if replace_pred(e)
replacer!(e)
end
if e isa Expr && recurse_pred(e)
for a in e.args
_expr_replace!(a, replace_pred, replacer!, recurse_pred)
end
replacer(e)
elseif e isa Expr && recurse_pred(e)
Expr(e.head, [_expr_replace(a, replace_pred, replacer, recurse_pred) for a in e.args]...)
end
end

function _to_iterspec(exs::Vector, is_generator::Bool)
if length(exs) === 1 && exs[1].head === :filter
@assert length(exs[1].args) >= 2
return Expr(:filter, _to_iterspec(exs[1].args[2:end], true), exs[1].args[1])
return if length(exs[1].args) >= 2
Expr(:filter, _to_iterspec(exs[1].args[2:end], true), exs[1].args[1])
else # invalid
Expr(:filter, exs[1].args[1])
end
end
outex = Expr(:iteration)
for e in exs
Expand All @@ -71,7 +73,7 @@ function _to_iterspec(exs::Vector, is_generator::Bool)
end
elseif e.head === :(=)
push!(outex.args, Expr(:in, e.args...))
else
else # invalid. TODO: at least find something that round-trips.
@assert false "unknown iterspec in $e"
end
end
Expand All @@ -80,7 +82,7 @@ end

"""
Return `e.args`, but with any parameters in SyntaxTree (flattened, source) order.
Parameters are expected to be as `e.args[pos]`.
Parameters are expected to be at `e.args[pos]`.

e.g. orderings of (a,b,c;d;e;f):
Expr: (tuple (parameters (parameters (parameters f) e) d) a b c)
Expand Down Expand Up @@ -253,14 +255,14 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
elseif e.head === :comparison
for i = 2:2:length(child_exprs)
op,op_esc = unwrap_esc(child_exprs[i])
@assert op isa Symbol
op_s = string(op)
if is_dotted_operator(op_s)
child_exprs[i] = Expr(:., op_esc(Symbol(op_s[2:end])))
if op isa Symbol
op_s = string(op)
if is_dotted_operator(op_s)
child_exprs[i] = Expr(:., op_esc(Symbol(op_s[2:end])))
end
end
end
elseif e.head === :macrocall
@assert nargs >= 2
elseif e.head === :macrocall && nargs >= 2
a1,a1_esc = unwrap_esc(e.args[1])
child_exprs = collect_expr_parameters(e, 3)
if child_exprs[2] isa LineNumberNode
Expand Down Expand Up @@ -289,8 +291,7 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
elseif a1.name === Symbol("@big_str")
end
end
elseif e.head === Symbol("'")
@assert nargs === 1
elseif e.head === Symbol("'") && nargs === 1
st_k = K"call"
child_exprs = Any[e.head, e.args[1]]
elseif e.head === :. && nargs === 2
Expand All @@ -302,11 +303,9 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
elseif a2 isa QuoteNode
child_exprs[2] = a2_esc(a2.value)
end
elseif e.head === :for
@assert nargs === 2
elseif e.head === :for && nargs === 2
child_exprs = Any[_to_iterspec(Any[e.args[1]], false), e.args[2]]
elseif e.head === :where
@assert nargs >= 2
elseif e.head === :where && nargs >= 2
e2,_ = unwrap_esc(e.args[2])
if !(e2 isa Expr && e2.head === :braces)
child_exprs = Any[e.args[1], Expr(:braces, e.args[2:end]...)]
Expand All @@ -315,7 +314,7 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
child_exprs = collect_expr_parameters(e, 1)
elseif e.head in (:curly, :ref)
child_exprs = collect_expr_parameters(e, 2)
elseif e.head === :try
elseif e.head === :try && nargs >= 3
child_exprs = Any[e.args[1]]
# Expr:
# (try (block ...) var (block ...) [block ...] [block ...])
Expand Down Expand Up @@ -343,22 +342,21 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
st_k = K"generator"
child_exprs = Any[]
next = e
while next.head === :flatten
@assert next.args[1].head === :generator
while next.head === :flatten && length(next.args) >= 1 && next.args[1].head === :generator
push!(child_exprs, _to_iterspec(next.args[1].args[2:end], true))
next = next.args[1].args[1]
end
@assert next.head === :generator
push!(child_exprs, _to_iterspec(next.args[2:end], true))
pushfirst!(child_exprs, next.args[1])
if next.head === :generator
push!(child_exprs, _to_iterspec(next.args[2:end], true))
pushfirst!(child_exprs, next.args[1])
end
elseif e.head === :ncat || e.head === :nrow
dim = unwrap_esc_(popfirst!(child_exprs))
st_flags |= JS.set_numeric_flags(dim)
elseif e.head === :typed_ncat
st_flags |= JS.set_numeric_flags(unwrap_esc_(e.args[2]))
deleteat!(child_exprs, 2)
elseif e.head === :(->)
@assert nargs === 2
elseif e.head === :(->) && nargs === 2
a1, a1_esc = unwrap_esc(e.args[1])
if a1 isa Expr && a1.head === :block
# Expr parsing fails to make :parameters here...
Expand Down Expand Up @@ -397,13 +395,12 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
src = maybe_extract_lnn(e.args[2], src)
child_exprs[2] = maybe_unwrap_arg(e.args[2])
end
elseif e.head === :module
@assert nargs === 3
if !e.args[1]
elseif e.head === :module && nargs === 3
if e.args[1] === false
st_flags |= JS.BARE_MODULE_FLAG
end
child_exprs = Any[e.args[2], e.args[3]]
elseif e.head === :do
elseif e.head === :do && nargs === 2
# Expr:
# (do (call f args...) (-> (tuple lam_args...) (block ...)))
# SyntaxTree:
Expand All @@ -421,21 +418,19 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
st_k = K"call"
end
child_exprs = Any[callargs..., Expr(:do_lambda, e.args[2].args...)]
elseif e.head === :let
if nargs >= 1
a1,_ = unwrap_esc(e.args[1])
if !(a1 isa Expr && a1.head === :block)
child_exprs[1] = Expr(:block, e.args[1])
end
elseif e.head === :let && nargs >= 1
a1,_ = unwrap_esc(e.args[1])
if !(a1 isa Expr && a1.head === :block)
child_exprs[1] = Expr(:block, e.args[1])
end
elseif e.head === :struct
elseif e.head === :struct && nargs >= 1
e.args[1] && (st_flags |= JS.MUTABLE_FLAG)
child_exprs = child_exprs[2:end]
# TODO handle docstrings after refactor
elseif (e.head === :using || e.head === :import)
_expr_replace!(e,
(e)->(e isa Expr && e.head === :.),
(e)->(e.head = :importpath))
e2 = _expr_replace(e, (e)->(e isa Expr && e.head === :.),
(e)->Expr(:importpath, e.args...))
child_exprs = e2.args
elseif e.head === :kw
st_k = K"="
elseif e.head in (:local, :global) && nargs > 1
Expand Down Expand Up @@ -463,36 +458,39 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
if e.args[1] isa Expr && e.args[1].head === :purity
st_k = K"meta"
child_exprs = [Expr(:quoted_symbol, :purity), Base.EffectsOverride(e.args[1].args...)]
else
@assert e.args[1] isa Symbol
if e.args[1] === :nospecialize
if nargs > 2
st_k = K"block"
# Kick the can down the road (should only be simple atoms?)
child_exprs = map(c->Expr(:meta, :nospecialize, c), child_exprs[2:end])
else
st_id, src = _insert_convert_expr(e.args[2], graph, src)
setmeta!(SyntaxTree(graph, st_id); nospecialize=true)
return st_id, src
end
elseif e.args[1] in (:inline, :noinline, :generated, :generated_only,
:max_methods, :optlevel, :toplevel, :push_loc, :pop_loc,
:no_constprop, :aggressive_constprop, :specialize, :compile, :infer,
:nospecializeinfer, :force_compile, :propagate_inbounds, :doc)
# TODO: Some need to be handled in lowering
for (i, ma) in enumerate(e.args)
if ma isa Symbol
# @propagate_inbounds becomes (meta inline
# propagate_inbounds), but usually(?) only args[1] is
# converted here
child_exprs[i] = Expr(:quoted_symbol, e.args[i])
end
elseif nargs === 0
# pass
elseif e.args[1] === :nospecialize
if nargs === 1
child_exprs[1] = Expr(:quoted_symbol, :nospecialize)
elseif nargs > 2
st_k = K"block"
# Kick the can down the road (should only be simple atoms?)
child_exprs = map(c->Expr(:meta, :nospecialize, c), child_exprs[2:end])
elseif nargs === 2
st_id, src = _insert_convert_expr(e.args[2], graph, src)
setmeta!(SyntaxTree(graph, st_id); nospecialize=true)
return st_id, src
end
elseif e.args[1] in (:inline, :noinline, :generated, :generated_only,
:max_methods, :optlevel, :toplevel, :push_loc, :pop_loc,
:no_constprop, :aggressive_constprop, :specialize, :compile, :infer,
:nospecializeinfer, :force_compile, :propagate_inbounds, :doc)
# TODO: Some need to be handled in lowering
for (i, ma) in enumerate(e.args)
if ma isa Symbol
# @propagate_inbounds becomes (meta inline
# propagate_inbounds), but usually(?) only args[1] is
# converted here
child_exprs[i] = Expr(:quoted_symbol, e.args[i])
end
else
# Can't throw a hard error; it is explicitly tested that meta can take arbitrary keys.
@error("Unknown meta form at $src: `$e`\n$(sprint(dump, e))")
child_exprs[1] = Expr(:quoted_symbol, e.args[1])
end
else
# Can't throw a hard error; it is explicitly tested that meta can
# take arbitrary keys.
@error("Unknown meta form at $src: `$e`\n$(sprint(dump, e))")
st_k = K"meta"
child_exprs[1] = Expr(:quoted_symbol, e.args[1])
end
elseif e.head === :scope_layer
@assert nargs === 2
Expand All @@ -501,27 +499,22 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
st_id, src = _insert_convert_expr(e.args[1], graph, src)
setattr!(graph, st_id, scope_layer=e.args[2])
return st_id, src
elseif e.head === :symbolicgoto || e.head === :symboliclabel
@assert nargs === 1
elseif e.head === :symbolicgoto || e.head === :symboliclabel && nargs === 1
st_k = e.head === :symbolicgoto ? K"symbolic_label" : K"symbolic_goto"
st_attrs[:name_val] = string(e.args[1])
child_exprs = nothing
elseif e.head in (:inline, :noinline)
@assert nargs === 1 && e.args[1] isa Bool
elseif e.head in (:inline, :noinline) && nargs === 1 && e.args[1] isa Bool
# TODO: JuliaLowering doesn't accept this (non-:meta) form yet
st_k = K"TOMBSTONE"
child_exprs = nothing
elseif e.head === :inbounds
@assert nargs === 1 && typeof(e.args[1]) in (Symbol, Bool)
elseif e.head === :inbounds && nargs === 1 && typeof(e.args[1]) in (Symbol, Bool)
# TODO: JuliaLowering doesn't accept this form yet
st_k = K"TOMBSTONE"
child_exprs = nothing
elseif e.head === :core
@assert nargs === 1
@assert e.args[1] isa Symbol
elseif e.head === :core && nargs === 1 && e.args[1] isa Symbol
st_attrs[:name_val] = string(e.args[1])
child_exprs = nothing
elseif e.head === :islocal || e.head === :isglobal
elseif (e.head === :islocal || e.head === :isglobal) && nargs === 1
st_k = K"extension"
child_exprs = [Expr(:quoted_symbol, e.head), e.args[1]]
elseif e.head === :block && nargs >= 1 &&
Expand Down Expand Up @@ -563,10 +556,12 @@ function _insert_convert_expr(@nospecialize(e), graph::SyntaxGraph, src::SourceA
end

#---------------------------------------------------------------------------
# Throw if this function isn't complete. Finally, insert a new node into the
# graph and recurse on child_exprs
# Omit tombstones. Unrecognized expr heads become K"expr_syntax". Finally,
# insert a new node into the graph and recurse on child_exprs
if st_k === K"None"
error("Unknown expr head at $src: `$(e.head)`\n$(sprint(dump, e))")
st_k = K"expr_syntax"
st_attrs[:value] = e
child_exprs = nothing
elseif st_k === K"TOMBSTONE"
return nothing, src
end
Expand Down
5 changes: 5 additions & 0 deletions src/kinds.jl
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Expand Up @@ -133,6 +133,11 @@ function _register_kinds()
"constdecl"
# Returned from statements that should error if the result is used.
"unused_only"
# Leaf kind denoting unquoted AST where `.value` is an Expr. Only
# used for compatibility with old-style macros called with arguments
# that have no other representation in SyntaxTree (e.g. head mapping
# to no kind, interpolations in strange places, etc).
"expr_syntax"
"END_LOWERING_KINDS"

# The following kinds are emitted by lowering and used in Julia's untyped IR
Expand Down
4 changes: 4 additions & 0 deletions src/macro_expansion.jl
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Expand Up @@ -517,6 +517,10 @@ function expand_forms_1(ctx::MacroExpansionContext, ex::SyntaxTree)
(expand_forms_1(ctx, a) for a in args)...
]
end
elseif k === K"expr_syntax"
throw(LoweringError(ex, "malformed Expr outside of macrocall or quote: \
check for macros producing unlowerable forms, \
or missing cases in `expr_to_syntaxtree`"))
elseif is_leaf(ex)
ex
elseif k == K"<:" || k == K">:" || k == K"-->"
Expand Down
13 changes: 13 additions & 0 deletions test/macros.jl
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Expand Up @@ -360,6 +360,19 @@ end
"""; expr_compat_mode=true)
@test test_mod.SOME_ENUM <: Enum
@test test_mod.X1 isa Enum

# Completely unknown expr heads are OK to produce from macro expansions as
# long as another macro cleans it up
Base.include_string(test_mod, """
macro unbungle(x)
:(1)
end

macro bungle()
esc(Expr(:macrocall, :var"@unbungle", @__LINE__, Expr(Symbol("what???"), 1, 2, 3)))
end""")

@test JuliaLowering.include_string(test_mod, "@bungle()"; expr_compat_mode=true) === 1
end

@testset "macros producing meta forms" begin
Expand Down
22 changes: 22 additions & 0 deletions test/macros_ir.jl
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Expand Up @@ -186,3 +186,25 @@ cmdmac`hello`
cmdmac`hello`12345
#---------------------
1 (return "hello from cmdmac with suffix 12345")

########################################
# @nospecialize (zero args)
function foo()
@nospecialize
end
#---------------------
1 (method TestMod.foo)
2 latestworld
3 TestMod.foo
4 (call core.Typeof %₃)
5 (call core.svec %₄)
6 (call core.svec)
7 SourceLocation::1:10
8 (call core.svec %₅ %₆ %₇)
9 --- method core.nothing %₈
slots: [slot₁/#self#(!read)]
1 (meta :nospecialize)
2 (return core.nothing)
10 latestworld
11 TestMod.foo
12 (return %₁₁)
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