Accommodate JuliaSyntax in tests

JuliaSyntax generates more consistent syntax trees for obscure versions
of long and short form anonymous function argument lists. For the cases
which are different and lead to errors, adjust the tests to use explicit
`Expr`s here so that we're testing ExprTools code rather than the Julia
parser itself.

* `function (x)::Integer; x end` is now parsed correctly
* Use an explicit Expr for the old `(;) -> nothing` syntax

test/function.jl

@@ -483,12 +483,16 @@ function_form(short::Bool) = string(short ? "short" : "long", "-form")
     @testset "block expression ($(function_form(short)) anonymous function)" for short in (true, false)
         @testset "(;)" begin
             # The `(;)` syntax was deprecated in 1.4.0-DEV.585 (ce29ec547e) but we can still
-            # test the behavior with `begin end`.
-            f, expr = if short
-                @audit (begin end) -> nothing
+            # test the behavior with an explicit Expr
+            expr = if short
+                # `(;) -> nothing`
+                Expr(:->, Expr(:block), Expr(:block, LineNumberNode(@__LINE__, @__FILE__), :nothing))
             else
-                @audit function (begin end) nothing end
+                # `function (;) nothing end`
+                Expr(:function, Expr(:block), Expr(:block, LineNumberNode(@__LINE__, @__FILE__), :nothing))
             end
+            f = eval(expr)
+
             @test length(methods(f)) == 1
             @test f() === nothing
 
@@ -788,8 +792,12 @@ function_form(short::Bool) = string(short ? "short" : "long", "-form")
 
     @testset "return-type (long-form anonymous function)" begin
         @testset "(x)::Integer" begin
-            # Interpreted as `function (x::Integer); x end`
-            f, expr = @audit function (x)::Integer; x end
+            # Older parsers interpret
+            #   `function (x)::Integer; x end`
+            # as 
+            #   `function (x::Integer); x end`
+            expr = Expr(:function, Expr(:tuple, Expr(:(::), :x, :Integer)), Expr(:block, LineNumberNode(@__LINE__, @__FILE__), :x))
+            f = eval(expr)
             @test length(methods(f)) == 1
             @test f(0) == 0
             @test_throws MethodError f(0.0)