Case bodies with certain expressions case macro-expansion time crash.

[arthurp]

@match crashes during macro expansion when applied to the following code (I'm using released v1.0.1 on Julia v1.0):

@match 1 begin _ => [] end

The error message is:

ERROR: LoadError: MethodError: no method matching union()
Closest candidates are:
  union(::Pkg.Pkg2.Pkg2Types.VersionSet, ::Pkg.Pkg2.Pkg2Types.VersionSet) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/Pkg2/types.jl:130
  union(::Pkg.Types.VersionSpec, ::Pkg.Types.VersionSpec) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/versions.jl:223
  union(::BitSet, ::Any...) at bitset.jl:272
  ...
Stacktrace:
 [1] getvars(::Array{Any,1}) at /home/amp/.julia/packages/Match/M8WAy/src/matchutils.jl:76
 [2] getvars(::Expr) at /home/amp/.julia/packages/Match/M8WAy/src/matchutils.jl:73
 [3] gen_match_expr(::Int64, ::Expr, ::Symbol, ::Bool) at /home/amp/.julia/packages/Match/M8WAy/src/matchmacro.jl:365
 [4] gen_match_expr(::Int64, ::Expr, ::Symbol) at /home/amp/.julia/packages/Match/M8WAy/src/matchmacro.jl:348
 [5] @match(::LineNumberNode, ::Module, ::Any, ::Any) at /home/amp/.julia/packages/Match/M8WAy/src/matchmacro.jl:434
in expression starting at none:1

It looks like getvars doesn't correctly handle the case where an Expr does not have any args. Specifically it calls union with one arg per element of args, so empty args means zero-arg union call, which is an error.

[thautwarm]

@arthurp It has been solved. Please close the issue.