Fix for detecting call heads in function signatures (#247)

Discovered parsing packages in General

Author: c42f

src/parse_stream.jl

@@ -527,20 +527,23 @@ Retroactively inspecting or modifying the parser's output can be confusing, so
 using this function should be avoided where possible.
 """
 function peek_behind(stream::ParseStream, pos::ParseStreamPosition)
-    if token_is_last(stream, pos) && !isempty(stream.tokens)
+    if token_is_last(stream, pos) && pos.token_index > 0
         t = stream.tokens[pos.token_index]
         return (kind=kind(t),
                 flags=flags(t),
                 orig_kind=t.orig_kind,
                 is_leaf=true)
-    elseif !isempty(stream.ranges)
+    elseif !isempty(stream.ranges) && pos.range_index > 0
         r = stream.ranges[pos.range_index]
         return (kind=kind(r),
                 flags=flags(r),
                 orig_kind=K"None",
                 is_leaf=false)
     else
-        internal_error("Can't peek behind at start of stream")
+        return (kind=K"None",
+                flags=EMPTY_FLAGS,
+                orig_kind=K"None",
+                is_leaf=true)
     end
 end
 
@@ -585,7 +588,11 @@ function first_child_position(stream::ParseStream, pos::ParseStreamPosition)
     end
 end
 
-function peek_behind(stream::ParseStream; skip_trivia::Bool=true)
+# Get last position in stream "of interest", skipping
+# * parens nodes
+# * deleted tokens (TOMBSTONE)
+# * whitespace (if skip_trivia=true)
+function peek_behind_pos(stream::ParseStream; skip_trivia::Bool=true)
     token_index = lastindex(stream.tokens)
     range_index = lastindex(stream.ranges)
     while range_index >= firstindex(stream.ranges) &&
@@ -601,11 +608,11 @@ function peek_behind(stream::ParseStream; skip_trivia::Bool=true)
         end
         token_index -= 1
     end
-    if token_index > 0
-        return peek_behind(stream, ParseStreamPosition(token_index, range_index))
-    else
-        internal_error("Can't peek behind at start of stream")
-    end
+    return ParseStreamPosition(token_index, range_index)
+end
+
+function peek_behind(stream::ParseStream; skip_trivia::Bool=true)
+    peek_behind(stream, peek_behind_pos(stream; skip_trivia=skip_trivia))
 end
 
 #-------------------------------------------------------------------------------

src/parser.jl

@@ -80,6 +80,10 @@ function peek_behind(ps::ParseState, args...; kws...)
     peek_behind(ps.stream, args...; kws...)
 end
 
+function peek_behind_pos(ps::ParseState, args...; kws...)
+    peek_behind_pos(ps.stream, args...; kws...)
+end
+
 function bump(ps::ParseState, flags=EMPTY_FLAGS; skip_newlines=nothing, kws...)
     skip_nl = isnothing(skip_newlines) ? ps.whitespace_newline : skip_newlines
     bump(ps.stream, flags; skip_newlines=skip_nl, kws...)
@@ -306,7 +310,7 @@ end
 # The expression is a call after stripping `where` and `::`
 function was_eventually_call(ps::ParseState)
     stream = ps.stream
-    p = position(ps)
+    p = peek_behind_pos(ps)
     while true
         b = peek_behind(stream, p)
         if b.kind == K"call"

test/parser.jl

@@ -589,6 +589,7 @@ tests = [
         "function (f() where T) where U end" => "(function (where (parens (where (call f) T)) U) (block))"
         "function (f()::S) end"=>  "(function (parens (::-i (call f) S)) (block))"         => Expr(:function, Expr(:(::), Expr(:call, :f), :S), Expr(:block))
         "function ((f()::S) where T) end" => "(function (parens (where (parens (::-i (call f) S)) T)) (block))"
+        "function (x*y ) end" => "(function (parens (call-i x * y)) (block))"
         # body
         "function f() \n a \n b end"  =>  "(function (call f) (block a b))"
         "function f() end"       =>  "(function (call f) (block))"