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Improve lowering of module / toplevel / import / using
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Lower `module`, `import` and `using` to an explicit runtime function
call rather than a bare expression. This imperative approach allows us
to remove module, import and using expressions from the lowered IR.

As part of this the `import` and `using` expressions have their syntax
checked by lowering rather than later in the runtime.

Lowering of `module` results in a quoted `toplevel` expression for later
consumption by `eval`. This expression also includes the standard
definitions of `eval()` and `import()` rather than having these defined
by a special lowering step at runtime.
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@c42f
c42f committed Apr 22, 2024
1 parent 85ee5c7 commit 5a95763
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Showing 10 changed files with 402 additions and 95 deletions.
20 changes: 11 additions & 9 deletions src/ast.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ function _makenode(graph::SyntaxGraph, srcref, head, children; attrs...)
return SyntaxTree(graph, id)
end

function makenode(ctx, srcref, head, children::SyntaxTree...; attrs...)
function makenode(ctx, srcref, head, children::Union{Nothing,SyntaxTree}...; attrs...)
_makenode(syntax_graph(ctx), srcref, head, _node_ids(children...); attrs...)
end

Expand Down Expand Up @@ -53,6 +53,13 @@ function makeleaf(ctx, srcref, kind)
_makenode(syntax_graph(ctx), srcref, kind, nothing)
end

function _match_srcref(ex)
if Meta.isexpr(ex, :macrocall) && ex.args[1] == Symbol("@HERE")
QuoteNode(ex.args[2])
else
esc(ex)
end
end

function _match_kind_ex(defs, srcref, ex)
kws = []
Expand All @@ -68,12 +75,7 @@ function _match_kind_ex(defs, srcref, ex)
end
if length(args) == 1
srcref = Symbol("srcref_$(length(defs))")
ref_ex = if Meta.isexpr(args[1], :macrocall) && args[1].args[1] == Symbol("@HERE")
QuoteNode(args[1].args[2])
else
esc(args[1])
end
push!(defs, :($srcref = $ref_ex))
push!(defs, :($srcref = $(_match_srcref(args[1]))))
elseif length(args) > 1
error("Unexpected: extra srcref argument in `$ex`?")
end
Expand Down Expand Up @@ -138,7 +140,7 @@ Any `kind` can be replaced with an expression of the form
* `kind(attr=val)` - set an additional attribute
* `kind(srcref; attr₁=val₁, attr₂=val₂)` - the general form
In any place `srcref` is used, the special form `@HERE` can be used to instead
In any place `srcref` is used, the special form `@HERE()` can be used to instead
to indicate that the "primary" location of the source is the location where
`@HERE` occurs.
Expand Down Expand Up @@ -170,7 +172,7 @@ to indicate that the "primary" location of the source is the location where
macro ast(ctx, srcref, tree)
defs = []
push!(defs, :(ctx = $(esc(ctx))))
push!(defs, :(srcref = $(esc(srcref))))
push!(defs, :(srcref = $(_match_srcref(srcref))))
ex = _expand_ast_tree(defs, :ctx, :srcref, tree)
quote
$(defs...)
Expand Down
177 changes: 172 additions & 5 deletions src/desugaring.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,18 +18,19 @@ end
struct DesugaringContext{GraphType} <: AbstractLoweringContext
graph::GraphType
next_var_id::Ref{VarId}
mod::Module
end

function DesugaringContext(ctx)
function DesugaringContext(ctx, mod)
graph = syntax_graph(ctx)
ensure_attributes!(graph,
kind=Kind, syntax_flags=UInt16, green_tree=GreenNode,
source_pos=Int, source=Union{SourceRef,NodeId},
source_pos=Int, source=SourceAttrType,
value=Any, name_val=String,
scope_type=Symbol, # :hard or :soft
var_id=VarId,
lambda_info=LambdaInfo)
DesugaringContext(freeze_attrs(graph), Ref{VarId}(1))
DesugaringContext(freeze_attrs(graph), Ref{VarId}(1), mod)
end

#-------------------------------------------------------------------------------
Expand Down Expand Up @@ -382,6 +383,154 @@ function expand_function_def(ctx, ex)
end
end

function _append_importpath(ctx, path_spec, path)
prev_was_dot = true
for component in children(path)
k = kind(component)
if k == K"quote"
# Permit quoted path components as in
# import A.(:b).:c
component = component[1]
end
@chk kind(component) in (K"Identifier", K".")
name = component.name_val
is_dot = kind(component) == K"."
if is_dot && !prev_was_dot
throw(LoweringError(component, "invalid import path: `.` in identifier path"))
end
prev_was_dot = is_dot
push!(path_spec, @ast(ctx, component, name::K"String"))
end
path_spec
end

function expand_import(ctx, ex)
is_using = kind(ex) == K"using"
if kind(ex[1]) == K":"
# import M: x.y as z, w
# (import (: (importpath M) (as (importpath x y) z) (importpath w)))
# =>
# (call module_import
# false
# (call core.svec "M")
# (call core.svec 2 "x" "y" "z" 1 "w" "w"))
@chk numchildren(ex[1]) >= 2
from = ex[1][1]
@chk kind(from) == K"importpath"
from_path = @ast ctx from [K"call"
"svec"::K"core"
_append_importpath(ctx, SyntaxList(ctx), from)...
]
paths = ex[1][2:end]
else
# import A.B
# (using (importpath A B))
# (call module_import true nothing (call core.svec 1 "w"))
@chk numchildren(ex) >= 1
from_path = nothing_(ctx, ex)
paths = children(ex)
end
path_spec = SyntaxList(ctx)
for path in paths
as_name = nothing
if kind(path) == K"as"
@chk numchildren(path) == 2
as_name = path[2]
@chk kind(as_name) == K"Identifier"
path = path[1]
end
@chk kind(path) == K"importpath"
push!(path_spec, @ast(ctx, path, numchildren(path)::K"Integer"))
_append_importpath(ctx, path_spec, path)
push!(path_spec, isnothing(as_name) ? nothing_(ctx, ex) :
@ast(ctx, as_name, as_name.name_val::K"String"))
end
@ast ctx ex [
K"call"
module_import ::K"Value"
ctx.mod ::K"Value"
is_using ::K"Value"
from_path
[K"call"
"svec"::K"core"
path_spec...
]
]
end

function expand_module(ctx::DesugaringContext, ex::SyntaxTree)
modname_ex = ex[1]
@chk kind(modname_ex) == K"Identifier"
modname = modname_ex.name_val

std_defs = if !has_flags(ex, JuliaSyntax.BARE_MODULE_FLAG)
@ast ctx (@HERE) [
K"block"
[K"using"
[K"importpath"
"Base" ::K"Identifier"
]
]
[K"function"
[K"call"
"eval" ::K"Identifier"
"x" ::K"Identifier"
]
[K"call"
"eval" ::K"core"
modname ::K"Identifier"
"x" ::K"Identifier"
]
]
[K"function"
[K"call"
"include" ::K"Identifier"
"x" ::K"Identifier"
]
[K"call"
"_call_latest" ::K"core"
"include" ::K"top"
modname ::K"Identifier"
"x" ::K"Identifier"
]
]
[K"function"
[K"call"
"include" ::K"Identifier"
[K"::"
"mapexpr" ::K"Identifier"
"Function" ::K"top"
]
"x" ::K"Identifier"
]
[K"call"
"_call_latest" ::K"core"
"include" ::K"top"
"mapexpr" ::K"Identifier"
modname ::K"Identifier"
"x" ::K"Identifier"
]
]
]
end

body = ex[2]
@chk kind(body) == K"block"

@ast ctx ex [
K"call"
eval_module ::K"Value"
ctx.mod ::K"Value"
modname ::K"String"
[K"inert"(body)
[K"toplevel"
std_defs
children(body)...
]
]
]
end

function expand_forms(ctx::DesugaringContext, ex::SyntaxTree)
k = kind(ex)
if k == K"call"
Expand Down Expand Up @@ -417,6 +566,24 @@ function expand_forms(ctx::DesugaringContext, ex::SyntaxTree)
"tuple"::K"core"
expand_forms(ctx, children(ex))...
]
elseif k == K"module"
# TODO: check-toplevel
expand_module(ctx, ex)
elseif k == K"import" || k == K"using"
# TODO: check-toplevel
expand_import(ctx, ex)
elseif k == K"export" || k == K"public"
TODO(ex)
elseif k == K"toplevel"
# The toplevel form can't be lowered here - it needs to just be quoted
# and passed through to a call to eval.
# TODO: check-toplevel
@ast ctx ex [
K"call"
eval ::K"Value"
ctx.mod ::K"Value"
[K"inert" ex]
]
elseif !haschildren(ex)
ex
else
Expand All @@ -438,8 +605,8 @@ function expand_forms(ctx::DesugaringContext, exs::Union{Tuple,AbstractVector})
res
end

function expand_forms(ex::SyntaxTree)
ctx = DesugaringContext(ex)
function expand_forms(mod::Module, ex::SyntaxTree)
ctx = DesugaringContext(ex, mod)
res = expand_forms(ctx, reparent(ctx, ex))
ctx, res
end
Expand Down
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