Try a line number workaround

Author: Drvi

src/include_test_file.jl

@@ -1,9 +1,10 @@
-using JuliaSyntax: ParseStream, @K_str, build_tree, bump_trivia, kind, parse!, peek_full_token, peek_token
+using JuliaSyntax: ParseError, ParseStream, @K_str, any_error, build_tree, bump_trivia, kind, last_byte, parse!, peek_full_token, peek_token
 using StringViews
 
 function include_test_file(ti_filter::TestItemFilter, path::String)
     bytes = read(path)
     stream = ParseStream(bytes)
+    line_starts = Int32[Int32(i) for (i, x) in enumerate(bytes) if x == 0x0a] # :(
     tls = task_local_storage()
     tls[:SOURCE_PATH] = path # This is also done by Base.include
     try
@@ -13,11 +14,12 @@ function include_test_file(ti_filter::TestItemFilter, path::String)
             k = kind(t)
             k == K"EndMarker" && break
             if k == K"@"
+                line = searchsortedfirst(line_starts, last_byte(stream))
                 tf = peek_full_token(stream, 2)
                 v = @inbounds @view(bytes[tf.first_byte:tf.last_byte])
-                if     v == b"testitem" ; _eval_from_stream(stream, path, ti_filter, bytes)
-                elseif v == b"testsetup"; _eval_from_stream(stream, path)
-                elseif v == b"test_rel" ; _eval_from_stream(stream, path, ti_filter)
+                if     v == b"testitem" ; _eval_from_stream(stream, path, line, ti_filter, bytes)
+                elseif v == b"testsetup"; _eval_from_stream(stream, path, line)
+                elseif v == b"test_rel" ; _eval_from_stream(stream, path, line, ti_filter)
                 else
                     error("Test files must only include `@testitem` and `@testsetup` calls, got an `@$(StringView(v))` at $(path)") # TODO
                 end
@@ -35,17 +37,17 @@ _contains(s::AbstractString, pattern::Regex) = occursin(pattern, s)
 _contains(s::AbstractString, pattern::AbstractString) = s == pattern
 
 # unconditionally eval
-function _eval_from_stream(stream, path)
+function _eval_from_stream(stream, path, line)
     parse!(stream; rule=:statement)
-    ast = build_tree(Expr, stream;  filename=path)
+    ast = build_tree(Expr, stream;  filename=path, first_line=line)
     Core.eval(Main, ast)
     return nothing
 end
 
 # test_rel -> apply ti_filter on the parsed ast
-function _eval_from_stream(stream, path, ti_filter::TestItemFilter)
+function _eval_from_stream(stream, path, line, ti_filter::TestItemFilter)
     parse!(stream; rule=:statement)
-    ast = build_tree(Expr, stream; filename=path)
+    ast = build_tree(Expr, stream; filename=path, first_line=line)
     any_error(stream) && throw(ParseError(stream, filename=path))
     filtered = __filter_rai(ti_filter, ast)::Union{Nothing, Expr}
     filtered === nothing || Core.eval(Main, filtered::Expr)
@@ -54,10 +56,10 @@ end
 
 # like above, but tries to avoid parsing the ast if it sees from the name identifier token
 # it won't pass the filter
-function _eval_from_stream(stream, path, ti_filter::TestItemFilter, bytes)
+function _eval_from_stream(stream, path, line, ti_filter::TestItemFilter, bytes)
     if ti_filter.name isa Nothing
         parse!(stream; rule=:statement)
-        ast = build_tree(Expr, stream; filename=path)
+        ast = build_tree(Expr, stream; filename=path, first_line=line)
         any_error(stream) && throw(ParseError(stream, filename=path))
         filtered = __filter_ti(ti_filter, ast)::Union{Nothing, Expr}
         filtered === nothing || Core.eval(Main, filtered::Expr)
@@ -68,7 +70,7 @@ function _eval_from_stream(stream, path, ti_filter::TestItemFilter, bytes)
     name = @inbounds StringView(@view(bytes[name_t.first_byte:name_t.last_byte]))
     parse!(stream; rule=:statement)
     if _contains(name, ti_filter.name)
-        ast = build_tree(Expr, stream; filename=path)
+        ast = build_tree(Expr, stream; filename=path, first_line=line)
         any_error(stream) && throw(ParseError(stream, filename=path))
         filtered = __filter_ti(ti_filter, ast)::Union{Nothing, Expr}
         filtered === nothing || Core.eval(Main, filtered::Expr)