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The mass of the concrete will probably damage both the fnec and the sned side at their lowest edges. The concrete will shrink, leaving a path for rainwater to penetrate down the entire lengths of the timber used for the shed & fence. Even if both are 'treated' timber they will rot in an accelerated timescale, as they will never dry out.
You can discourage unwanted guests by planting a thorny blackberry bush, and training the stems along the top of the fence and shed roof.
Is there anything wrong with pouring concrete between the shed and the fence? As an added layer of fuckyou?