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support old-style macros #21

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support old-style macros #21

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e427498
support old-style macros
ericphanson Jul 31, 2025
67b12f0
Update src/macro_expansion.jl
ericphanson Jul 31, 2025
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12 changes: 10 additions & 2 deletions src/macro_expansion.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -145,8 +145,16 @@ function expand_macro(ctx, ex)
end
macro_invocation_world = Base.get_world_counter()
expanded = try
# TODO: Allow invoking old-style macros for compat
invokelatest(macfunc, macro_args...)
if applicable(macfunc, macro_args...)
invokelatest(macfunc, macro_args...)
else
# try old-style macro
args = [Expr(x) for x in macro_args[2:end]]
line, _ = source_location(macname)
file = filename(macname)
line_number_node = Base.LineNumberNode(line, file)
invokelatest(macfunc, line_number_node, ctx.current_layer.mod, args...)
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@c42f c42f Jul 31, 2025

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Ah right. So this approach doesn't work if the old macro returns an AST, because that AST will be Expr but the macro expander (and subsequent lowering) is expecting a SyntaxTree.

In that case we need full bidirectional Expr <--> SyntaxTree support. And also need a solution for handling hygiene which is represented rather differently in the two cases. See my WIP branch for how to do those :-)

end
catch exc
if exc isa MacroExpansionError
# Add context to the error.
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6 changes: 6 additions & 0 deletions test/macros.jl
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Expand Up @@ -142,4 +142,10 @@ end == [
"2"
]

# old-style generated macro, e.g. as lowered by pre-JuliaLowering lowering
@eval test_mod var"@hi"(__source__::LineNumberNode, __module__::Module) = "hi"

# check that we can macroexpand it properly even though we don't have the new method
# that accepts a MacroExpansionContext
@test JuliaLowering.include_string(test_mod, "@hi") == "hi"
end