From 51622b5d4a3ad89b0cb09257fa722a1046eaa9f8 Mon Sep 17 00:00:00 2001
From: Markus Kurtz <kurtz@mathematik.uni-kl.de>
Date: Mon, 3 Jul 2023 13:48:36 +0200
Subject: [PATCH] Use MacroTools

---
 src/misc/VarNames.jl | 74 +++++++++++++++++++++++---------------------
 1 file changed, 39 insertions(+), 35 deletions(-)

diff --git a/src/misc/VarNames.jl b/src/misc/VarNames.jl
index a72abfab4e..8a1922b4b5 100644
--- a/src/misc/VarNames.jl
+++ b/src/misc/VarNames.jl
@@ -1,4 +1,4 @@
-using Base.Iterators
+import MacroTools as MT
 
 @assert VarName === Union{Symbol, AbstractString, Char}
 const VarShape = Union{Missing, Int, Tuple{Vararg{Int}}}
@@ -94,6 +94,34 @@ _reshape(iter, ::Missing) = popfirst!(iter)
 _reshape(iter, n::Int) = collect(Iterators.take(iter, n))
 _reshape(iter, dims::Tuple{Vararg{Int}}) = reshape(collect(Iterators.take(iter, prod(dims))), dims)
 
+function _varname_interface(e::Expr, @nospecialize s::Union{Expr, Symbol})
+    ex = MT.isexpr(e, :(=), :function) ? e : Expr(:(=), e, :())
+    d = MT.splitdef(ex)
+
+    callf = esc(d[:name])
+    f = esc(MT.postwalk(x -> MT.@capture(x, a_.b_) ? b : x, d[:name]))
+    wheres = esc.(d[:whereparams])
+
+    args = d[:args][begin:end-1]
+    splitargs = MacroTools.splitarg.(args)
+    args = esc.(args)
+    req(all(((_, _, slurp, default),) -> (slurp, default) === (false, nothing), splitargs),
+        "Default and slurp arguments currently not supported")
+    req(isempty(d[:kwargs]), "Keyword arguments currently not supported")
+    argnames = first.(splitargs)
+    req(all(!isnothing, argnames), "Nameless arguments currently not supported")
+    argnames = esc.(argnames)
+
+    s = esc(s)
+    argtypes = esc.(a[2] for a in splitargs)
+    argtypes = :(Tuple{$(argtypes...), $s} where {$(wheres...)})
+    base = f == callf ?
+        :(req(hasmethod($f, $argtypes), "base method of `$($f)` for $($argtypes) missing")) :
+        :($f($(args...), s::$s; kv...) where {$(wheres...)} = $callf($(argnames...), s; kv...))
+
+    return f, args, argnames, wheres, base
+end
+
 @doc raw"""
     @varnames_interface [M.]f(args..., varnames)
 
@@ -172,10 +200,10 @@ julia> v = [1,4,1]; @f "variable dims" x[v...]; x
 ```
 """
 macro varnames_interface(e::Expr, options...)
-    f, args, argnames, base = _varname_interface(e, :(Vector{Symbol}))
+    f, args, argnames, wheres, base = _varname_interface(e, :(Vector{Symbol}))
     fancy_method = quote
-        $f($(args...), s::VarNames...; kv...) = $f($(args...), s; kv...)
-        function $f($(args...), s::Tuple{Vararg{VarNames}}; kv...)
+        $f($(args...), s::VarNames...; kv...) where {$(wheres...)} = $f($(argnames...), s; kv...)
+        function $f($(args...), s::Tuple{Vararg{VarNames}}; kv...) where {$(wheres...)}
             X, gens = $f($(argnames...), variable_names(s...); kv...)
             return X, reshape_to_varnames(gens, s...)...
         end
@@ -191,7 +219,7 @@ macro varnames_interface(e::Expr, options...)
     end
 
     n isa Symbol || return :($base; $fancy_method)
-    fancy_n_method = :($f($(args...), $n::Int, s::VarName=:x; kv...) = $f($(argnames...), Symbol.(s, $en); kv...))
+    fancy_n_method = :($f($(args...), $n::Int, s::VarName=:x; kv...) where {$(wheres...)} = $f($(argnames...), Symbol.(s, $en); kv...))
 
     opts[:macros] === :(:no) && return :($base; $fancy_method; $fancy_n_method)
     ss, xs = opts[:macros] === :(:all) ? (:(s::Union{Expr, Symbol}...), :(_expr_pairs(s))) :
@@ -211,26 +239,10 @@ macro varnames_interface(e::Expr, options...)
     return :($base; $fancy_method; $fancy_n_method; $fancy_macro)
 end
 
-function _varname_interface(e::Expr, @nospecialize s::Union{Expr, Symbol})
-    req(Base.isexpr(e, :call), "Argument `$e` must be a function call")
-    callf = esc(e.args[1])
-    f = esc(unqualified(e.args[1]))
-    # TODO cope with `where` clause, (and perhaps with optional arguments and keyvalues)
-    args = e.args[2:end-1]
-    argnames = esc.(argname.(args))
-    argtypes = Expr(:curly, :Tuple, argtype.(args)..., s)
-    args = esc.(args)
-    base = f == callf ?
-        :(req(hasmethod($f, $argtypes), "base method of `$($f)` for $($argtypes) missing")) :
-        :($f($(args...), s::$s; kv...) = $callf($(argnames...), s; kv...))
-    return f, args, argnames, base
-end
-
 function parse_options(kvs::Tuple{Vararg{Expr}}, default::Dict{Symbol}, valid::Dict{Symbol, <:Vector} = Dict{Symbol, Vector{Any}}())
     result = Dict{Symbol, Any}(default)
     for o in kvs
-        req(Base.isexpr(o, :(=), 2), "only key value options allowed")
-        k, v = o.args
+        MT.@capture(o, k_ = v_) || error("only key value options allowed")
         req(k in keys(result), "invalid key value option key `$k`")
         k in keys(valid) && req(v in valid[k], "invalid option `$v` to key `$k`")
         result[k] = v
@@ -238,16 +250,9 @@ function parse_options(kvs::Tuple{Vararg{Expr}}, default::Dict{Symbol}, valid::D
     return result
 end
 
-unqualified(a::Symbol) = a
-unqualified(e::Expr) = (req(Base.isexpr(e, :., 2), "Not a name: `$e`"); e.args[2].value) :: Symbol
-argname(a::Symbol) = a
-argname(e::Expr) = (req(Base.isexpr(e, :(::), 2), "Not a (possibly type asserted) Symbol: `$e`"); e.args[1]) :: Symbol
-argtype(a::Symbol) = :Any
-argtype(e::Expr) = (req(Base.isexpr(e, :(::)), "Not a type assertion or Symbol: `$e`"); e.args[end]) :: Union{Expr, Symbol}
-
-_expr_pairs(a::Tuple{Vararg{Union{Expr, Symbol}}}) = _expr_pair.(a)
-_expr_pairs((a,)::Tuple{Expr}) = Base.isexpr(a, :tuple) ? _expr_pair.(a.args) : (_expr_pair(a),) # for `@f args... (varnames...)` variant
-_expr_pair(e::Expr) = (req(Base.isexpr(e, :ref), "variable name must be like `x` or `x[...]`, not `$e`"); e.args[1] => Expr(:tuple, esc.(e.args[2:end])...))
+_expr_pairs(es::Tuple{Vararg{Union{Expr, Symbol}}}) = _expr_pair.(es)
+_expr_pairs((e,)::Tuple{Expr}) = MT.@capture(e, (es__,)) ? _expr_pair.(es) : (_expr_pair(e),) # for `@f args... (varnames...,)` variant
+_expr_pair(e::Expr) = MT.@capture(e, x_[a__]) ? x => :($(esc.(a)...),) : error("variable name must be like `x` or `x[...]`, not `$e`")
 _expr_pair(s::Symbol) = s => missing
 
 @doc raw"""
@@ -294,8 +299,8 @@ julia> x
 ```
 """
 macro varname_interface(e::Expr)
-    f, args, argnames, base = _varname_interface(e, :Symbol)
-    fancy_method = :($f($(args...), s::Union{AbstractString, Char}; kv...) = $f($(argnames...), Symbol(s); kv...))
+    f, args, argnames, wheres, base = _varname_interface(e, :Symbol)
+    fancy_method = :($f($(args...), s::Union{AbstractString, Char}; kv...) where {$(wheres...)} = $f($(argnames...), Symbol(s); kv...))
     fancy_macro = :(
         macro $f($(argnames...), s::Symbol)
             quote
@@ -330,4 +335,3 @@ polynomial_ring(R::Ring, s::Symbol; kv...) = invoke(polynomial_ring, Tuple{NCRin
 polynomial_ring(R::Ring, s::Union{AbstractString, Char}; kv...) = polynomial_ring(R, Symbol(s); kv...)
 
 # TODO: weights in `graded_polynomial_ring` and `power_series_ring`
-# TODO: Cope with Julia 1.6 not having `isexpr`. Maybe use MacroTools.