if !check.validType0(pos, t.Origin().fromRHS, append(nest, t), append(path, t)) {
			return false
		}

		// see TODO above
		// check.valids.add(t) // t is valid

	case *TypeParam:
		// A type parameter stands for the type (argument) it was instantiated with.
		// Check the corresponding type argument for validity if we are in an
		// instantiated type.
		if d := len(nest) - 1; d >= 0 {
			inst := nest[d] // the type instance

		P := NewTypeName(nopos, nil, "P", nil)    // [P ~string | []byte]
		makeSig(NewTypeParam(P, NewInterfaceType(nil, []Type{u})))
	}
}

func TestIssue51093(t *testing.T) {
	// Each test stands for a conversion of the form P(val)
	// where P is a type parameter with typ as constraint.
	// The test ensures that P(val) has the correct type P
	// and is not a constant.
	var tests = []struct {
		typ string

must either all be present or all be absent. If present, each name
stands for one item (parameter or result) of the specified type and
all non-<a href="#Blank_identifier">blank</a> names in the signature
must be <a href="#Uniqueness_of_identifiers">unique</a>.
If absent, each type stands for one item of that type.
Parameter and result
lists are always parenthesized except that if there is exactly

			t.Fatalf("got %v, want %s", p, want)
		}
	}()
	LookupFieldOrMethod(nil, false, nil, "")
}

func TestLookupFieldOrMethod(t *testing.T) {
	// Test cases assume a lookup of the form a.f or x.f, where a stands for an
	// addressable value, and x for a non-addressable value (even though a variable
	// for ease of test case writing).
	var tests = []struct {
		src      string
		found    bool
		index    []int

must either all be present or all be absent. If present, each name
stands for one item (parameter or result) of the specified type and
all non-<a href="#Blank_identifier">blank</a> names in the signature
must be <a href="#Uniqueness_of_identifiers">unique</a>.
If absent, each type stands for one item of that type.
Parameter and result
lists are always parenthesized except that if there is exactly