Ensure SlotNumbers are assigned when deciding top of signature (#25)

Fixes timholy/Revise.jl#422

Author: timholy

src/LoweredCodeUtils.jl

@@ -455,6 +455,14 @@ function get_running_name(@nospecialize(recurse), frame, pc, name, parentname)
         return name, pc, nothing
     end
     pctop, isgen = nameinfo
+    # Sometimes signature_top---which follows SSAValue links backwards to find the first
+    # line needed to define the signature---misses out on a SlotNumber assignment.
+    # Fix https://github.com/timholy/Revise.jl/issues/422
+    stmt = pc_expr(frame, pctop)
+    while pctop > 1 && isa(stmt, SlotNumber) && !isassigned(frame.framedata.locals, pctop)
+        pctop -= 1
+        stmt = pc_expr(frame, pctop)
+    end   # end fix
     sigtparent, lastpcparent = signature(recurse, frame, pctop)
     sigtparent === nothing && return name, pc, lastpcparent
     methparent = whichtt(sigtparent)

test/runtests.jl

@@ -13,6 +13,13 @@ struct Caller end
 struct Gen{T} end
 end
 
+# Stuff for https://github.com/timholy/Revise.jl/issues/422
+module Lowering422
+const LVec{N, T} = NTuple{N, Base.VecElement{T}}
+const LT{T} = Union{LVec{<:Any, T}, T}
+const FloatingTypes = Union{Float32, Float64}
+end
+
 bodymethtest0(x) = 0
 function bodymethtest0(x)
     y = 2x
@@ -324,4 +331,22 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     @test length(ks) == 2
     @test dct[ks[1]] == dct[ks[2]]
     @test isdefined(Lowering, ks[1]) || isdefined(Lowering, ks[2])
+
+    # https://github.com/timholy/Revise.jl/issues/422
+    ex = :(@generated function fneg(x::T) where T<:LT{<:FloatingTypes}
+         s = """
+         %2 = fneg $(llvm_type(T)) %0
+         ret $(llvm_type(T)) %2
+         """
+         return :(
+             $(Expr(:meta, :inline));
+             Base.llvmcall($s, T, Tuple{T}, x)
+         )
+     end)
+    empty!(signatures)
+    Core.eval(Lowering422, ex)
+    frame = JuliaInterpreter.prepare_thunk(Lowering422, ex)
+    rename_framemethods!(frame)
+    pc = methoddefs!(signatures, frame; define=false)
+    @test typeof(Lowering422.fneg) ∈ Set(Base.unwrap_unionall(sig).parameters[1] for sig in signatures)
 end