Add @check and @should_not_warn.

src/Traceur.jl

@@ -6,11 +6,12 @@ using MacroTools
 
 import Core.MethodInstance
 
-export @trace, @trace_static
+export @trace, @trace_static, @should_not_warn, @check
 
 include("util.jl")
 include("analysis.jl")
 include("trace.jl")
 # include("trace_static.jl")
+include("check.jl")
 
 end # module

src/analysis.jl

@@ -70,9 +70,11 @@ struct Warning
   call::Call
   line::Int
   message::String
+  stack::Vector{Call}
 end
 
 Warning(call, message) = Warning(call, -1, message)
+Warning(call, line, message) = Warning(call, line, message, Call[])
 
 function warning_printer()
   (w) -> begin

src/check.jl

@@ -0,0 +1,40 @@
+const should_not_warn = Set{Function}()
+
+# this is only a macro to avoid parens around function definitions:
+# @should_not_warn
+# function foo(x)
+#   ...
+# end
+macro should_not_warn(expr)
+  quote
+    fun = $(esc(expr))
+    push!(should_not_warn, fun)
+    fun
+  end
+end
+
+"""
+    check(f::Function)
+
+Run Traceur on f, and throw an error if any warnings occur inside functions tagged with @should_not_warn.
+"""
+function check(f)
+  failed = false
+  wp = warning_printer()
+  result = trace(f) do warning
+    ix = findfirst((call) -> call.f in should_not_warn, warning.stack)
+    if ix != nothing
+      tagged_function = warning.stack[ix].f
+      message = "$(warning.message) (called from $(tagged_function))"
+      warning = Warning(warning.call, warning.line, message, warning.stack)
+      wp(warning)
+      failed = true
+    end
+  end
+  @assert !failed "One or more warnings occured inside functions tagged with @should_not_warn"
+  result
+end
+
+macro check(expr)
+  :(check(() -> $(esc(expr))))
+end

src/trace.jl

@@ -4,25 +4,35 @@ Cassette.@context TraceurCtx
 
 struct Trace
   seen::Set
+  stack::Vector{Call}
   warn
 end
 
-Trace(w) = Trace(Set(), w)
+Trace(w) = Trace(Set(), Vector{Call}(), w)
 
 isprimitive(f) = f isa Core.Builtin || f isa Core.IntrinsicFunction
 
 const ignored_methods = Set([@which((1,2)[1])])
 const ignored_functions = Set([getproperty, setproperty!])
 
-function Cassette.posthook(ctx::TraceurCtx, out, f, args...)
-  C, T = DynamicCall(f, args...), typeof.((f, args))
+function Cassette.prehook(ctx::TraceurCtx, f, args...)
   tra = ctx.metadata
-  (f ∈ ignored_functions || T ∈ tra.seen || isprimitive(f) ||
-    method(C) ∈ ignored_methods || method(C).module ∈ (Core, Core.Compiler)) && return nothing
+  C = DynamicCall(f, args...)
+  push!(tra.stack, C)
+  nothing
+end
 
-  push!(tra.seen, T)
-  analyse((a...) -> tra.warn(Warning(a...)), C)
-  return nothing
+function Cassette.posthook(ctx::TraceurCtx, out, f, args...)
+  tra = ctx.metadata
+  C = tra.stack[end]
+  T = typeof.((f, args))
+  if !(f ∈ ignored_functions || T ∈ tra.seen || isprimitive(f) ||
+       method(C) ∈ ignored_methods || method(C).module ∈ (Core, Core.Compiler))
+    push!(tra.seen, T)
+    analyse((a...) -> tra.warn(Warning(a..., copy(tra.stack))), C)
+  end
+  pop!(tra.stack)
+  nothing
 end
 
 trace(w, f) = Cassette.overdub(TraceurCtx(metadata=Trace(w)), f)

test/runtests.jl

@@ -52,6 +52,12 @@ function test(warnings)
   @test isempty(ws)
 end
 
+x = 1
+
+my_add(y) = x + y
+
+@should_not_warn my_stable_add(y) = my_add(y)
+
 @testset "Traceur" begin
   @testset "Dynamic" begin
     test(Traceur.warnings)
@@ -61,4 +67,7 @@ end
   # end
   # @test_nowarn @trace naive_sum(1.0)
   # @test_nowarn @trace_static naive_sum(1.0)
+
+  @test_nowarn @check my_add(1)
+  @test_throws AssertionError @check my_stable_add(1)
 end