In early exit, check signature for exact match (#17)

Fixes timholy/Revise.jl#318

Author: timholy

src/LoweredCodeUtils.jl

@@ -37,7 +37,8 @@ function getcallee(stmt)
     error(stmt, " is not a call expression")
 end
 
-ismethod(frame::Frame) = ismethod(pc_expr(frame))
+ismethod(frame::Frame)  = ismethod(pc_expr(frame))
+ismethod3(frame::Frame) = ismethod3(pc_expr(frame))
 ismethod(stmt)  = isexpr(stmt, :method)
 ismethod1(stmt) = isexpr(stmt, :method, 1)
 ismethod3(stmt) = isexpr(stmt, :method, 3)
@@ -356,7 +357,7 @@ function methoddef!(@nospecialize(recurse), signatures, frame::Frame, @nospecial
         end
         sigt, pc = signature(recurse, frame, stmt, pc)
         meth = whichtt(sigt)
-        if meth === nothing && define
+        if (meth === nothing || !(meth.sig <: sigt && sigt <: meth.sig)) && define
             step_expr!(recurse, frame, stmt, true)
             meth = whichtt(sigt)
         end

test/runtests.jl

@@ -250,4 +250,14 @@ bodymethtest5(x, y=Dict(1=>2)) = 5
     @test startswith(String(bodymethod(first(methods(bodymethtest3))).name), "#")
     @test bodymethod(first(methods(bodymethtest4))).nargs == 3  # one extra for #self#
     @test bodymethod(first(methods(bodymethtest5))).nargs == 3
+
+    ex = :(typedsig(x) = 1)
+    frame = JuliaInterpreter.prepare_thunk(Lowering, ex)
+    methoddefs!(signatures, frame; define=true)
+    ex = :(typedsig(x::Int) = 2)
+    frame = JuliaInterpreter.prepare_thunk(Lowering, ex)
+    JuliaInterpreter.next_until!(LoweredCodeUtils.ismethod3, frame, true)
+    empty!(signatures)
+    methoddefs!(signatures, frame; define=true)
+    @test first(signatures).parameters[end] == Int
 end