Function branch

assertion/function/functioncontracts/infer.go:318–336

branch reports whether we can make a branch and learn nilness from the true and false successor. The function returns equal, not-equal successor and the binary operation iff (1) b ends with an equality or inequality comparison; (2) the operands can have nil as a valid value; Otherwise, the funct

(b *ssa.BasicBlock)

//
// Otherwise, the function returns all nil.
func branch(b *ssa.BasicBlock) (*ssa.BasicBlock, *ssa.BasicBlock, *ssa.BinOp) {
	ifInstr, ok := b.Instrs[len(b.Instrs)-1].(*ssa.If)
	if !ok {
		return nil, nil, nil
	}
	binOp, ok := ifInstr.Cond.(*ssa.BinOp)
	// Check only one operand is sufficient since the two operands must have the same type.
	if !ok || typeshelper.TypeBarsNilness(binOp.X.Type()) {
		// not a binary comparison or the type cannot have nil as a value.
		return nil, nil, nil
	}
	switch binOp.Op {
	case token.EQL:
		return b.Succs[0], b.Succs[1], binOp
	case token.NEQ:
		return b.Succs[1], b.Succs[0], binOp
	}
	return nil, nil, nil
}

// isBuiltinAppendCall reports if the call is a call to builtin append.
func isBuiltinAppendCall(v *ssa.Call) bool {