Don't scan for 3-arg method if there is none (#91)

This is the primary portion of the fix for
timholy/Revise.jl#758

Author: timholy

src/signatures.jl

@@ -506,6 +506,19 @@ function methoddef!(@nospecialize(recurse), signatures, frame::Frame, @nospecial
         Base.invokelatest(error, "given invalid definition: ", stmt)
     end
     name = name::Symbol
+    # Is there any 3-arg method definition with the same name? If not, avoid risk of executing code that
+    # we shouldn't (fixes https://github.com/timholy/Revise.jl/issues/758)
+    found = false
+    for i = pc+1:length(framecode.src.code)
+        newstmt = framecode.src.code[i]
+        if ismethod3(newstmt)
+            if ismethod_with_name(framecode.src, newstmt, string(name))
+                found = true
+                break
+            end
+        end
+    end
+    found || return nothing
     while true  # methods containing inner methods may need multiple trips through this loop
         sigt, pc = signature(recurse, frame, stmt, pc)
         stmt = pc_expr(frame, pc)

src/utils.jl

@@ -96,6 +96,8 @@ function ismethod_with_name(src, stmt, target::AbstractString; reentrant::Bool=f
             isdone = true
         end
     end
+    # On Julia 1.6 we have to add escaping (CBinding makes function names like "(S)")
+    target = escape_string(target, "()")
     return match(Regex("(^|#)$target(\$|#)"), string(name)) !== nothing
 end