Fix an infinite loop when "backing up" to the signature

Author: timholy

src/CodeTracking.jl

@@ -198,9 +198,11 @@ function definition(method::Method, ::Type{String})
     end
     # The function declaration was presumably on a previous line
     lineindex = lastindex(linestarts)
-    while !isfuncexpr(ex)
+    while !isfuncexpr(ex) && lineindex > 0
         istart = linestarts[lineindex]
         ex, iend = Meta.parse(src, istart)
+        lineindex -= 1
+        line -= 1
     end
     return src[istart:iend-1]
 end

test/runtests.jl

@@ -11,18 +11,19 @@ isdefined(Main, :Revise) ? includet("script.jl") : include("script.jl")
     file, line = whereis(m)
     scriptpath = normpath(joinpath(@__DIR__, "script.jl"))
     @test file == scriptpath
-    @test line == 3
+    @test line == 4
     trace = try
         call_throws()
     catch
         stacktrace(catch_backtrace())
     end
-    @test whereis(trace[2]) == (scriptpath, 10)
+    @test whereis(trace[2]) == (scriptpath, 11)
     @test whereis(trace[3]) === nothing
 
     src = definition(m, String)
     @test src == """
     function f1(x, y)
+        # A comment
         return x + y
     end
     """

test/script.jl

@@ -1,5 +1,6 @@
 # NOTE: tests are sensitive to the line number at which statements appear
 function f1(x, y)
+    # A comment
     return x + y
 end