The 7.0 branch (and HEAD) behaves differently to 7.0.1 on this modules:

{-# LANGUAGE TemplateHaskell #-}
module Foo where

import Language.Haskell.TH

x :: Int
x = let args = [| show $(varE (mkName "x")) |]
    in undefined

1. 0.1 accepted it, while we now get:

Foo.hs:7:19:
    Ambiguous type variable `a0' in the constraint:
      (Show a0) arising from a use of `show'
    Probable fix: add a type signature that fixes these type variable(s)
    In the Template Haskell quotation [| show ($(varE (mkName "x"))) |]
    In the expression: [| show ($(varE (mkName "x"))) |]
    In an equation for `args': args = [| show ($(varE (mkName "x"))) |]

This affects these packages:

CCA
Printf-TH
grammar-combinators
hacanon-light
hamlet
rowrecord
th-lift
web-routes-quasi