minor code quality improvements (#446)

src/breakpoints.jl

@@ -165,7 +165,9 @@ function framecode_matches_breakpoint(framecode::FrameCode, bp::BreakpointFileLo
             return false
         end
     else
-        path, _ = whereis(framecode, 1)
+        w = whereis(framecode, 1)
+        w === nothing && return false
+        path, _ = w
         path = CodeTracking.maybe_fix_path(path)
         ispath(path) && (path = realpath(path))
 
@@ -186,7 +188,6 @@ function shouldbreak(frame::Frame, pc::Int)
 end
 
 function prepare_slotfunction(framecode::FrameCode, body::Union{Symbol,Expr})
-    ismeth = framecode.scope isa Method
     uslotnames = Set{Symbol}()
     slotnames  = Symbol[]
     for name in framecode.src.slotnames
@@ -223,13 +224,14 @@ function prepare_slotfunction(framecode::FrameCode, body::Union{Symbol,Expr})
         push!(assignments, :($maxexsym = $maxexpr))
         push!(assignments, :($slotname = $maxexsym > 0 ? something($dataname.locals[$maxexsym]) : $default))
     end
-    if ismeth
-        syms = sparam_syms(framecode.scope)
+    scope = framecode.scope
+    if isa(scope, Method)
+        syms = sparam_syms(scope)
         for i = 1:length(syms)
             push!(assignments, Expr(:(=), syms[i], :($dataname.sparams[$i])))
         end
     end
-    funcname = ismeth ? gensym("slotfunction") : gensym(Symbol(framecode.scope, "_slotfunction"))
+    funcname = isa(scope, Method) ? gensym("slotfunction") : gensym(Symbol(scope, "_slotfunction"))
     return Expr(:function, Expr(:call, funcname, framename), Expr(:block, assignments..., body))
 end
 

src/interpret.jl

@@ -282,7 +282,7 @@ end
 function structname(frame, node)
     name = node.args[1]
     if isa(name, GlobalRef)
-        mod = name.module
+        mod = name.mod
         name = name.name
     else
         mod = moduleof(frame)
@@ -489,7 +489,7 @@ function step_expr!(@nospecialize(recurse), frame, @nospecialize(node), istoplev
                 elseif node.head === :const
                     g = node.args[1]
                     if isa(g, GlobalRef)
-                        mod, name = g.module, g.name
+                        mod, name = g.mod, g.name
                     else
                         mod, name = moduleof(frame), g::Symbol
                     end

src/utils.jl

@@ -299,7 +299,11 @@ function lineoffset(framecode::FrameCode)
     return offset
 end
 
-getline(ln) = Int(isexpr(ln, :line) ? ln.args[1] : ln.line)::Int
+function getline(ln::Union{LineTypes,Expr})
+    _getline(ln::LineTypes) = ln.line
+    _getline(ln::Expr)      = ln.args[1] # assuming ln.head === :line
+    return Int(_getline(ln))::Int
+end
 # work around compiler error on 1.2
 @static if v"1.2.0" <= VERSION < v"1.3"
     getfile(ln) = begin
@@ -317,7 +321,11 @@ getline(ln) = Int(isexpr(ln, :line) ? ln.args[1] : ln.line)::Int
         CodeTracking.maybe_fixup_stdlib_path(path)
     end
 else
-    getfile(ln) = CodeTracking.maybe_fixup_stdlib_path(String(isexpr(ln, :line) ? ln.args[2] : ln.file)::String)
+    function getfile(ln::Union{LineTypes,Expr})
+        _getfile(ln::LineTypes) = ln.file::Symbol
+        _getfile(ln::Expr)      = ln.args[2]::Symbol # assuming ln.head === :line
+        return CodeTracking.maybe_fixup_stdlib_path(String(_getfile(ln)))
+    end
 end
 
 function firstline(ex::Expr)