assert: reject wrapped signed values in EqualValues

[lowgame]

Summary

Prevent EqualValues from treating a negative signed integer as an equal unsigned integer after wrapping conversion.

Changes

• Return unequal before numeric conversion when one operand is a negative signed integer and the other is unsigned.
• Add regression cases for both operand orders.

Motivation

ObjectsAreEqualValues(int64(-1), uint64(math.MaxUint64)) and the reverse order both returned true. The size-based numeric conversion converted -1 to MaxUint64, creating a false positive even though the numeric values differ.

Before the fix:

$ go test ./assert -run '^TestObjectsAreEqualValues$' -count=1
--- FAIL: TestObjectsAreEqualValues
    --- FAIL: TestObjectsAreEqualValues/ObjectsAreEqualValues(-1,_0xffffffffffffffff)
    --- FAIL: TestObjectsAreEqualValues/ObjectsAreEqualValues(0xffffffffffffffff,_-1)
FAIL

After the fix:

$ go test ./assert -run '^TestObjectsAreEqualValues$' -count=1
ok github.com/stretchr/testify/assert

$ go test ./assert -count=1
ok github.com/stretchr/testify/assert

$ GOTOOLCHAIN=go1.25.0 ./.ci.gogenerate.sh
passed

$ GOTOOLCHAIN=go1.25.0 ./.ci.gofmt.sh
passed

$ GOTOOLCHAIN=go1.25.0 ./.ci.govet.sh
passed

$ GOTOOLCHAIN=go1.25.0 go test -race ./...
passed (all packages)

Related issues

No related issue found.