Don't assume that SubString has pointer and copy instead (#506)

* Don't assume that `SubString` has `pointer` and copy instead

* Still assume `Substring{String}` has `pointer`

* Test with `Test.GenericString`

src/parse_stream.jl

@@ -391,7 +391,7 @@ function ParseStream(text::String, index::Integer=1; version=VERSION)
     ParseStream(unsafe_wrap(Vector{UInt8}, text),
                 text, index, version)
 end
-function ParseStream(text::SubString, index::Integer=1; version=VERSION)
+function ParseStream(text::SubString{String}, index::Integer=1; version=VERSION)
     # See also IOBuffer(SubString("x"))
     ParseStream(unsafe_wrap(Vector{UInt8}, pointer(text), sizeof(text)),
                 text, index, version)

test/parse_stream.jl

@@ -7,7 +7,8 @@ using JuliaSyntax: ParseStream,
     peek, peek_token,
     bump, bump_trivia, bump_invisible,
     emit, emit_diagnostic, TRIVIA_FLAG, INFIX_FLAG,
-    ParseStreamPosition, first_child_position, last_child_position
+    ParseStreamPosition, first_child_position, last_child_position,
+    parsestmt
 
 # Here we manually issue parse events in the order the Julia parser would issue
 # them
@@ -147,3 +148,13 @@ end
     @test first_child_position(st, position(st)) == ParseStreamPosition(4, 1)
     @test last_child_position(st, position(st)) == ParseStreamPosition(7, 2)
 end
+
+@testset "SubString{GenericString} (issue #505)" begin
+    x = Test.GenericString("1 2")
+    @test x == "1 2"
+    y = split(x)[1]
+    @test y == "1"
+    @test y isa SubString{GenericString}
+    @test ParseStream(y) isa ParseStream
+    @test parsestmt(Expr, y) == parsestmt(Expr, "1")
+end